diff --git a/slixmpp/xmlstream/stanzabase.py b/slixmpp/xmlstream/stanzabase.py
index 7679f73a..2f2faa8d 100644
--- a/slixmpp/xmlstream/stanzabase.py
+++ b/slixmpp/xmlstream/stanzabase.py
@@ -1,4 +1,3 @@
-
 # slixmpp.xmlstream.stanzabase
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 # module implements a wrapper layer for XML objects
@@ -11,13 +10,34 @@ from __future__ import annotations
 import copy
 import logging
 import weakref
-from typing import Optional
+from typing import (
+    cast,
+    Any,
+    Callable,
+    ClassVar,
+    Coroutine,
+    Dict,
+    List,
+    Iterable,
+    Optional,
+    Set,
+    Tuple,
+    Type,
+    TYPE_CHECKING,
+    Union,
+)
+from weakref import ReferenceType
 from xml.etree import ElementTree as ET
 
+from slixmpp.types import JidStr
 from slixmpp.xmlstream import JID
 from slixmpp.xmlstream.tostring import tostring
 
 
+if TYPE_CHECKING:
+    from slixmpp.xmlstream import XMLStream
+
+
 log = logging.getLogger(__name__)
 
 
@@ -28,7 +48,8 @@ XML_TYPE = type(ET.Element('xml'))
 XML_NS = 'http://www.w3.org/XML/1998/namespace'
 
 
-def register_stanza_plugin(stanza, plugin, iterable=False, overrides=False):
+def register_stanza_plugin(stanza: Type[ElementBase], plugin: Type[ElementBase],
+                           iterable: bool = False, overrides: bool = False) -> None:
     """
     Associate a stanza object as a plugin for another stanza.
 
@@ -85,15 +106,15 @@ def register_stanza_plugin(stanza, plugin, iterable=False, overrides=False):
             stanza.plugin_overrides[interface] = plugin.plugin_attrib
 
 
-def multifactory(stanza, plugin_attrib):
+def multifactory(stanza: Type[ElementBase], plugin_attrib: str) -> Type[ElementBase]:
     """
     Returns a ElementBase class for handling reoccuring child stanzas
     """
 
-    def plugin_filter(self):
+    def plugin_filter(self: Multi) -> Callable[..., bool]:
         return lambda x: isinstance(x, self._multistanza)
 
-    def plugin_lang_filter(self, lang):
+    def plugin_lang_filter(self: Multi, lang: Optional[str]) -> Callable[..., bool]:
         return lambda x: isinstance(x, self._multistanza) and \
                          x['lang'] == lang
 
@@ -101,31 +122,41 @@ def multifactory(stanza, plugin_attrib):
         """
         Template class for multifactory
         """
-        def setup(self, xml=None):
-            self.xml = ET.Element('')
+        _multistanza: Type[ElementBase]
 
-    def get_multi(self, lang=None):
-        parent = self.parent()
+        def setup(self, xml: Optional[ET.Element] = None) -> bool:
+            self.xml = ET.Element('')
+            return False
+
+    def get_multi(self: Multi, lang: Optional[str] = None) -> List[ElementBase]:
+        parent = fail_without_parent(self)
         if not lang or lang == '*':
             res = filter(plugin_filter(self), parent)
         else:
-            res = filter(plugin_filter(self, lang), parent)
+            res = filter(plugin_lang_filter(self, lang), parent)
         return list(res)
 
-    def set_multi(self, val, lang=None):
-        parent = self.parent()
+    def set_multi(self: Multi, val: Iterable[ElementBase], lang: Optional[str] = None) -> None:
+        parent = fail_without_parent(self)
         del_multi = getattr(self, 'del_%s' % plugin_attrib)
         del_multi(lang)
         for sub in val:
             parent.append(sub)
 
-    def del_multi(self, lang=None):
-        parent = self.parent()
+    def fail_without_parent(self: Multi) -> ElementBase:
+        parent = None
+        if self.parent:
+            parent = self.parent()
+        if not parent:
+            raise ValueError('No stanza parent for multifactory')
+        return parent
+
+    def del_multi(self: Multi, lang: Optional[str] = None) -> None:
+        parent = fail_without_parent(self)
         if not lang or lang == '*':
-            res = filter(plugin_filter(self), parent)
+            res = list(filter(plugin_filter(self), parent))
         else:
-            res = filter(plugin_filter(self, lang), parent)
-        res = list(res)
+            res = list(filter(plugin_lang_filter(self, lang), parent))
         if not res:
             del parent.plugins[(plugin_attrib, None)]
             parent.loaded_plugins.remove(plugin_attrib)
@@ -149,7 +180,8 @@ def multifactory(stanza, plugin_attrib):
     return Multi
 
 
-def fix_ns(xpath, split=False, propagate_ns=True, default_ns=''):
+def fix_ns(xpath: str, split: bool = False, propagate_ns: bool = True,
+           default_ns: str = '') -> Union[str, List[str]]:
     """Apply the stanza's namespace to elements in an XPath expression.
 
     :param string xpath: The XPath expression to fix with namespaces.
@@ -275,12 +307,12 @@ class ElementBase(object):
     #: The XML tag name of the element, not including any namespace
     #: prefixes. For example, an :class:`ElementBase` object for
     #: ``<message />`` would use ``name = 'message'``.
-    name = 'stanza'
+    name: ClassVar[str] = 'stanza'
 
     #: The XML namespace for the element. Given ``<foo xmlns="bar" />``,
     #: then ``namespace = "bar"`` should be used. The default namespace
     #: is ``jabber:client`` since this is being used in an XMPP library.
-    namespace = 'jabber:client'
+    namespace: str = 'jabber:client'
 
     #: For :class:`ElementBase` subclasses which are intended to be used
     #: as plugins, the ``plugin_attrib`` value defines the plugin name.
@@ -290,7 +322,7 @@ class ElementBase(object):
     #:     register_stanza_plugin(Message, FooPlugin)
     #:     msg = Message()
     #:     msg['foo']['an_interface_from_the_foo_plugin']
-    plugin_attrib = 'plugin'
+    plugin_attrib: ClassVar[str] = 'plugin'
 
     #: For :class:`ElementBase` subclasses that are intended to be an
     #: iterable group of items, the ``plugin_multi_attrib`` value defines
@@ -300,29 +332,29 @@ class ElementBase(object):
     #:     # Given stanza class Foo, with plugin_multi_attrib = 'foos'
     #:     parent['foos']
     #:     filter(isinstance(item, Foo), parent['substanzas'])
-    plugin_multi_attrib = ''
+    plugin_multi_attrib: ClassVar[str] = ''
 
     #: The set of keys that the stanza provides for accessing and
     #: manipulating the underlying XML object. This set may be augmented
     #: with the :attr:`plugin_attrib` value of any registered
     #: stanza plugins.
-    interfaces = {'type', 'to', 'from', 'id', 'payload'}
+    interfaces: ClassVar[Set[str]] = {'type', 'to', 'from', 'id', 'payload'}
 
     #: A subset of :attr:`interfaces` which maps interfaces to direct
     #: subelements of the underlying XML object. Using this set, the text
     #: of these subelements may be set, retrieved, or removed without
     #: needing to define custom methods.
-    sub_interfaces = set()
+    sub_interfaces: ClassVar[Set[str]] = set()
 
     #: A subset of :attr:`interfaces` which maps the presence of
     #: subelements to boolean values. Using this set allows for quickly
     #: checking for the existence of empty subelements like ``<required />``.
     #:
     #: .. versionadded:: 1.1
-    bool_interfaces = set()
+    bool_interfaces: ClassVar[Set[str]] = set()
 
     #: .. versionadded:: 1.1.2
-    lang_interfaces = set()
+    lang_interfaces: ClassVar[Set[str]] = set()
 
     #: In some cases you may wish to override the behaviour of one of the
     #: parent stanza's interfaces. The ``overrides`` list specifies the
@@ -336,7 +368,7 @@ class ElementBase(object):
     #: be affected.
     #:
     #: .. versionadded:: 1.0-Beta5
-    overrides = []
+    overrides: ClassVar[List[str]] = []
 
     #: If you need to add a new interface to an existing stanza, you
     #: can create a plugin and set ``is_extension = True``. Be sure
@@ -346,7 +378,7 @@ class ElementBase(object):
     #: parent stanza will be passed to the plugin directly.
     #:
     #: .. versionadded:: 1.0-Beta5
-    is_extension = False
+    is_extension: ClassVar[bool] = False
 
     #: A map of interface operations to the overriding functions.
     #: For example, after overriding the ``set`` operation for
@@ -355,15 +387,15 @@ class ElementBase(object):
     #:     {'set_body': <some function>}
     #:
     #: .. versionadded: 1.0-Beta5
-    plugin_overrides = {}
+    plugin_overrides: ClassVar[Dict[str, str]] = {}
 
     #: A mapping of the :attr:`plugin_attrib` values of registered
     #: plugins to their respective classes.
-    plugin_attrib_map = {}
+    plugin_attrib_map: ClassVar[Dict[str, Type[ElementBase]]] = {}
 
     #: A mapping of root element tag names (in ``'{namespace}elementname'``
     #: format) to the plugin classes responsible for them.
-    plugin_tag_map = {}
+    plugin_tag_map: ClassVar[Dict[str, Type[ElementBase]]] = {}
 
     #: The set of stanza classes that can be iterated over using
     #: the 'substanzas' interface. Classes are added to this set
@@ -372,17 +404,26 @@ class ElementBase(object):
     #:     register_stanza_plugin(DiscoInfo, DiscoItem, iterable=True)
     #:
     #: .. versionadded:: 1.0-Beta5
-    plugin_iterables = set()
+    plugin_iterables: ClassVar[Set[Type[ElementBase]]] = set()
 
     #: The default XML namespace: ``http://www.w3.org/XML/1998/namespace``.
-    xml_ns = XML_NS
+    xml_ns: ClassVar[str] = XML_NS
 
-    def __init__(self, xml=None, parent=None):
+    plugins: Dict[Tuple[str, Optional[str]], ElementBase]
+    #: The underlying XML object for the stanza. It is a standard
+    #: :class:`xml.etree.ElementTree` object.
+    xml: ET.Element
+    _index: int
+    loaded_plugins: Set[str]
+    iterables: List[ElementBase]
+    tag: str
+    parent: Optional[ReferenceType[ElementBase]]
+
+    def __init__(self, xml: Optional[ET.Element] = None, parent: Union[Optional[ElementBase], ReferenceType[ElementBase]] = None):
         self._index = 0
 
-        #: The underlying XML object for the stanza. It is a standard
-        #: :class:`xml.etree.ElementTree` object.
-        self.xml = xml
+        if xml is not None:
+            self.xml = xml
 
         #: An ordered dictionary of plugin stanzas, mapped by their
         #: :attr:`plugin_attrib` value.
@@ -419,7 +460,7 @@ class ElementBase(object):
                                  existing_xml=child,
                                  reuse=False)
 
-    def setup(self, xml=None):
+    def setup(self, xml: Optional[ET.Element] = None) -> bool:
         """Initialize the stanza's XML contents.
 
         Will return ``True`` if XML was generated according to the stanza's
@@ -429,29 +470,31 @@ class ElementBase(object):
         :param xml: An existing XML object to use for the stanza's content
                     instead of generating new XML.
         """
-        if self.xml is None:
+        if hasattr(self, 'xml'):
+            return False
+        if not hasattr(self, 'xml') and xml is not None:
             self.xml = xml
-
-        last_xml = self.xml
-        if self.xml is None:
-            # Generate XML from the stanza definition
-            for ename in self.name.split('/'):
-                new = ET.Element("{%s}%s" % (self.namespace, ename))
-                if self.xml is None:
-                    self.xml = new
-                else:
-                    last_xml.append(new)
-                last_xml = new
-            if self.parent is not None:
-                self.parent().xml.append(self.xml)
-
-            # We had to generate XML
-            return True
-        else:
-            # We did not generate XML
             return False
 
-    def enable(self, attrib, lang=None):
+
+        # Generate XML from the stanza definition
+        last_xml = ET.Element('')
+        for ename in self.name.split('/'):
+            new = ET.Element("{%s}%s" % (self.namespace, ename))
+            if not hasattr(self, 'xml'):
+                self.xml = new
+            else:
+                last_xml.append(new)
+            last_xml = new
+        if self.parent is not None:
+            parent = self.parent()
+            if parent:
+                parent.xml.append(self.xml)
+
+        # We had to generate XML
+        return True
+
+    def enable(self, attrib: str, lang: Optional[str] = None) -> ElementBase:
         """Enable and initialize a stanza plugin.
 
         Alias for :meth:`init_plugin`.
@@ -487,7 +530,10 @@ class ElementBase(object):
             else:
                 return None if check else self.init_plugin(name, lang)
 
-    def init_plugin(self, attrib, lang=None, existing_xml=None, element=None, reuse=True):
+    def init_plugin(self, attrib: str, lang: Optional[str] = None,
+                    existing_xml: Optional[ET.Element] = None,
+                    reuse: bool = True,
+                    element: Optional[ElementBase] = None) -> ElementBase:
         """Enable and initialize a stanza plugin.
 
         :param string attrib: The :attr:`plugin_attrib` value of the
@@ -525,7 +571,7 @@ class ElementBase(object):
 
         return plugin
 
-    def _get_stanza_values(self):
+    def _get_stanza_values(self) -> Dict[str, Any]:
         """Return A JSON/dictionary version of the XML content
         exposed through the stanza's interfaces::
 
@@ -567,7 +613,7 @@ class ElementBase(object):
             values['substanzas'] = iterables
         return values
 
-    def _set_stanza_values(self, values):
+    def _set_stanza_values(self, values: Dict[str, Any]) -> ElementBase:
         """Set multiple stanza interface values using a dictionary.
 
         Stanza plugin values may be set using nested dictionaries.
@@ -623,7 +669,7 @@ class ElementBase(object):
                         plugin.values = value
         return self
 
-    def __getitem__(self, full_attrib):
+    def __getitem__(self, full_attrib: str) -> Any:
         """Return the value of a stanza interface using dict-like syntax.
 
         Example::
@@ -688,7 +734,7 @@ class ElementBase(object):
         else:
             return ''
 
-    def __setitem__(self, attrib, value):
+    def __setitem__(self, attrib: str, value: Any) -> Any:
         """Set the value of a stanza interface using dictionary-like syntax.
 
         Example::
@@ -773,7 +819,7 @@ class ElementBase(object):
                 plugin[full_attrib] = value
         return self
 
-    def __delitem__(self, attrib):
+    def __delitem__(self, attrib: str) -> Any:
         """Delete the value of a stanza interface using dict-like syntax.
 
         Example::
@@ -851,7 +897,7 @@ class ElementBase(object):
                 pass
         return self
 
-    def _set_attr(self, name, value):
+    def _set_attr(self, name: str, value: Optional[JidStr]) -> None:
         """Set the value of a top level attribute of the XML object.
 
         If the new value is None or an empty string, then the attribute will
@@ -868,7 +914,7 @@ class ElementBase(object):
                 value = str(value)
             self.xml.attrib[name] = value
 
-    def _del_attr(self, name):
+    def _del_attr(self, name: str) -> None:
         """Remove a top level attribute of the XML object.
 
         :param name: The name of the attribute.
@@ -876,7 +922,7 @@ class ElementBase(object):
         if name in self.xml.attrib:
             del self.xml.attrib[name]
 
-    def _get_attr(self, name, default=''):
+    def _get_attr(self, name: str, default: str = '') -> str:
         """Return the value of a top level attribute of the XML object.
 
         In case the attribute has not been set, a default value can be
@@ -889,7 +935,8 @@ class ElementBase(object):
         """
         return self.xml.attrib.get(name, default)
 
-    def _get_sub_text(self, name, default='', lang=None):
+    def _get_sub_text(self, name: str, default: str = '',
+                      lang: Optional[str] = None) -> Union[str, Dict[str, str]]:
         """Return the text contents of a sub element.
 
         In case the element does not exist, or it has no textual content,
@@ -900,7 +947,7 @@ class ElementBase(object):
         :param default: Optional default to return if the element does
                         not exists. An empty string is returned otherwise.
         """
-        name = self._fix_ns(name)
+        name = cast(str, self._fix_ns(name))
         if lang == '*':
             return self._get_all_sub_text(name, default, None)
 
@@ -924,8 +971,9 @@ class ElementBase(object):
             return result
         return default
 
-    def _get_all_sub_text(self, name, default='', lang=None):
-        name = self._fix_ns(name)
+    def _get_all_sub_text(self, name: str, default: str = '',
+                          lang: Optional[str] = None) -> Dict[str, str]:
+        name = cast(str, self._fix_ns(name))
 
         default_lang = self.get_lang()
         results = {}
@@ -935,10 +983,16 @@ class ElementBase(object):
                 stanza_lang = stanza.attrib.get('{%s}lang' % XML_NS,
                                                 default_lang)
                 if not lang or lang == '*' or stanza_lang == lang:
-                    results[stanza_lang] = stanza.text
+                    if stanza.text is None:
+                        text = default
+                    else:
+                        text = stanza.text
+                    results[stanza_lang] = text
         return results
 
-    def _set_sub_text(self, name, text=None, keep=False, lang=None):
+    def _set_sub_text(self, name: str, text: Optional[str] = None,
+                      keep: bool = False,
+                      lang: Optional[str] = None) -> Optional[ET.Element]:
         """Set the text contents of a sub element.
 
         In case the element does not exist, a element will be created,
@@ -959,15 +1013,16 @@ class ElementBase(object):
             lang = default_lang
 
         if not text and not keep:
-            return self._del_sub(name, lang=lang)
+            self._del_sub(name, lang=lang)
+            return None
 
-        path = self._fix_ns(name, split=True)
+        path = cast(List[str], self._fix_ns(name, split=True))
         name = path[-1]
-        parent = self.xml
+        parent: Optional[ET.Element] = self.xml
 
         # The first goal is to find the parent of the subelement, or, if
         # we can't find that, the closest grandparent element.
-        missing_path = []
+        missing_path: List[str] = []
         search_order = path[:-1]
         while search_order:
             parent = self.xml.find('/'.join(search_order))
@@ -1008,15 +1063,17 @@ class ElementBase(object):
         parent.append(element)
         return element
 
-    def _set_all_sub_text(self, name, values, keep=False, lang=None):
-        self._del_sub(name, lang)
+    def _set_all_sub_text(self, name: str, values: Dict[str, str],
+                          keep: bool = False,
+                          lang: Optional[str] = None) -> None:
+        self._del_sub(name, lang=lang)
         for value_lang, value in values.items():
             if not lang or lang == '*' or value_lang == lang:
                 self._set_sub_text(name, text=value,
                                          keep=keep,
                                          lang=value_lang)
 
-    def _del_sub(self, name, all=False, lang=None):
+    def _del_sub(self, name: str, all: bool = False, lang: Optional[str] = None) -> None:
         """Remove sub elements that match the given name or XPath.
 
         If the element is in a path, then any parent elements that become
@@ -1034,11 +1091,11 @@ class ElementBase(object):
         if not lang:
             lang = default_lang
 
-        parent = self.xml
+        parent: Optional[ET.Element] = self.xml
         for level, _ in enumerate(path):
             # Generate the paths to the target elements and their parent.
             element_path = "/".join(path[:len(path) - level])
-            parent_path = "/".join(path[:len(path) - level - 1])
+            parent_path: Optional[str] = "/".join(path[:len(path) - level - 1])
 
             elements = self.xml.findall(element_path)
             if parent_path == '':
@@ -1061,7 +1118,7 @@ class ElementBase(object):
                 # after deleting the first level of elements.
                 return
 
-    def match(self, xpath):
+    def match(self, xpath: Union[str, List[str]]) -> bool:
         """Compare a stanza object with an XPath-like expression.
 
         If the XPath matches the contents of the stanza object, the match
@@ -1127,7 +1184,7 @@ class ElementBase(object):
         # Everything matched.
         return True
 
-    def get(self, key, default=None):
+    def get(self, key: str, default: Optional[Any] = None) -> Any:
         """Return the value of a stanza interface.
 
         If the found value is None or an empty string, return the supplied
@@ -1144,7 +1201,7 @@ class ElementBase(object):
             return default
         return value
 
-    def keys(self):
+    def keys(self) -> List[str]:
         """Return the names of all stanza interfaces provided by the
         stanza object.
 
@@ -1158,7 +1215,7 @@ class ElementBase(object):
             out.append('substanzas')
         return out
 
-    def append(self, item):
+    def append(self, item: Union[ET.Element, ElementBase]) -> ElementBase:
         """Append either an XML object or a substanza to this stanza object.
 
         If a substanza object is appended, it will be added to the list
@@ -1189,7 +1246,7 @@ class ElementBase(object):
 
         return self
 
-    def appendxml(self, xml):
+    def appendxml(self, xml: ET.Element) -> ElementBase:
         """Append an XML object to the stanza's XML.
 
         The added XML will not be included in the list of
@@ -1200,7 +1257,7 @@ class ElementBase(object):
         self.xml.append(xml)
         return self
 
-    def pop(self, index=0):
+    def pop(self, index: int = 0) -> ElementBase:
         """Remove and return the last substanza in the list of
         iterable substanzas.
 
@@ -1212,11 +1269,11 @@ class ElementBase(object):
         self.xml.remove(substanza.xml)
         return substanza
 
-    def next(self):
+    def next(self) -> ElementBase:
         """Return the next iterable substanza."""
         return self.__next__()
 
-    def clear(self):
+    def clear(self) -> ElementBase:
         """Remove all XML element contents and plugins.
 
         Any attribute values will be preserved.
@@ -1229,7 +1286,7 @@ class ElementBase(object):
         return self
 
     @classmethod
-    def tag_name(cls):
+    def tag_name(cls) -> str:
         """Return the namespaced name of the stanza's root element.
 
         The format for the tag name is::
@@ -1241,29 +1298,32 @@ class ElementBase(object):
         """
         return "{%s}%s" % (cls.namespace, cls.name)
 
-    def get_lang(self, lang=None):
+    def get_lang(self, lang: Optional[str] = None) -> str:
         result = self.xml.attrib.get('{%s}lang' % XML_NS, '')
-        if not result and self.parent and self.parent():
-            return self.parent()['lang']
+        if not result and self.parent:
+            parent = self.parent()
+            if parent:
+                return cast(str, parent['lang'])
         return result
 
-    def set_lang(self, lang):
+    def set_lang(self, lang: Optional[str]) -> None:
         self.del_lang()
         attr = '{%s}lang' % XML_NS
         if lang:
             self.xml.attrib[attr] = lang
 
-    def del_lang(self):
+    def del_lang(self) -> None:
         attr = '{%s}lang' % XML_NS
         if attr in self.xml.attrib:
             del self.xml.attrib[attr]
 
-    def _fix_ns(self, xpath, split=False, propagate_ns=True):
+    def _fix_ns(self, xpath: str, split: bool = False,
+                propagate_ns: bool = True) -> Union[str, List[str]]:
         return fix_ns(xpath, split=split,
                              propagate_ns=propagate_ns,
                              default_ns=self.namespace)
 
-    def __eq__(self, other):
+    def __eq__(self, other: Any) -> bool:
         """Compare the stanza object with another to test for equality.
 
         Stanzas are equal if their interfaces return the same values,
@@ -1290,7 +1350,7 @@ class ElementBase(object):
         # must be equal.
         return True
 
-    def __ne__(self, other):
+    def __ne__(self, other: Any) -> bool:
         """Compare the stanza object with another to test for inequality.
 
         Stanzas are not equal if their interfaces return different values,
@@ -1300,16 +1360,16 @@ class ElementBase(object):
         """
         return not self.__eq__(other)
 
-    def __bool__(self):
+    def __bool__(self) -> bool:
         """Stanza objects should be treated as True in boolean contexts.
         """
         return True
 
-    def __len__(self):
+    def __len__(self) -> int:
         """Return the number of iterable substanzas in this stanza."""
         return len(self.iterables)
 
-    def __iter__(self):
+    def __iter__(self) -> ElementBase:
         """Return an iterator object for the stanza's substanzas.
 
         The iterator is the stanza object itself. Attempting to use two
@@ -1318,7 +1378,7 @@ class ElementBase(object):
         self._index = 0
         return self
 
-    def __next__(self):
+    def __next__(self) -> ElementBase:
         """Return the next iterable substanza."""
         self._index += 1
         if self._index > len(self.iterables):
@@ -1326,13 +1386,16 @@ class ElementBase(object):
             raise StopIteration
         return self.iterables[self._index - 1]
 
-    def __copy__(self):
+    def __copy__(self) -> ElementBase:
         """Return a copy of the stanza object that does not share the same
         underlying XML object.
         """
-        return self.__class__(xml=copy.deepcopy(self.xml), parent=self.parent)
+        return self.__class__(
+            xml=copy.deepcopy(self.xml),
+            parent=self.parent,
+        )
 
-    def __str__(self, top_level_ns=True):
+    def __str__(self, top_level_ns: bool = True) -> str:
         """Return a string serialization of the underlying XML object.
 
         .. seealso:: :ref:`tostring`
@@ -1343,12 +1406,33 @@ class ElementBase(object):
         return tostring(self.xml, xmlns='',
                         top_level=True)
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         """Use the stanza's serialized XML as its representation."""
         return self.__str__()
 
     # Compatibility.
     _get_plugin = get_plugin
+    get_stanza_values = _get_stanza_values
+    set_stanza_values = _set_stanza_values
+
+    #: A JSON/dictionary version of the XML content exposed through
+    #: the stanza interfaces::
+    #:
+    #:     >>> msg = Message()
+    #:     >>> msg.values
+    #:    {'body': '', 'from': , 'mucnick': '', 'mucroom': '',
+    #:     'to': , 'type': 'normal', 'id': '', 'subject': ''}
+    #:
+    #: Likewise, assigning to the :attr:`values` will change the XML
+    #: content::
+    #:
+    #:     >>> msg = Message()
+    #:     >>> msg.values = {'body': 'Hi!', 'to': 'user@example.com'}
+    #:     >>> msg
+    #:     '<message to="user@example.com"><body>Hi!</body></message>'
+    #:
+    #: Child stanzas are exposed as nested dictionaries.
+    values = property(_get_stanza_values, _set_stanza_values)  # type: ignore
 
 
 class StanzaBase(ElementBase):
@@ -1386,9 +1470,14 @@ class StanzaBase(ElementBase):
 
     #: The default XMPP client namespace
     namespace = 'jabber:client'
+    types: ClassVar[Set[str]] = set()
 
-    def __init__(self, stream=None, xml=None, stype=None,
-                 sto=None, sfrom=None, sid=None, parent=None, recv=False):
+    def __init__(self, stream: Optional[XMLStream] = None,
+                 xml: Optional[ET.Element] = None,
+                 stype: Optional[str] = None,
+                 sto: Optional[JidStr] = None, sfrom: Optional[JidStr] = None,
+                 sid: Optional[str] = None,
+                 parent: Optional[ElementBase] = None, recv: bool = False):
         self.stream = stream
         if stream is not None:
             self.namespace = stream.default_ns
@@ -1403,7 +1492,7 @@ class StanzaBase(ElementBase):
             self['id'] = sid
         self.tag = "{%s}%s" % (self.namespace, self.name)
 
-    def set_type(self, value):
+    def set_type(self, value: str) -> StanzaBase:
         """Set the stanza's ``'type'`` attribute.
 
         Only type values contained in :attr:`types` are accepted.
@@ -1414,11 +1503,11 @@ class StanzaBase(ElementBase):
             self.xml.attrib['type'] = value
         return self
 
-    def get_to(self):
+    def get_to(self) -> JID:
         """Return the value of the stanza's ``'to'`` attribute."""
         return JID(self._get_attr('to'))
 
-    def set_to(self, value):
+    def set_to(self, value: JidStr) -> None:
         """Set the ``'to'`` attribute of the stanza.
 
         :param value: A string or :class:`slixmpp.xmlstream.JID` object
@@ -1426,11 +1515,11 @@ class StanzaBase(ElementBase):
         """
         return self._set_attr('to', str(value))
 
-    def get_from(self):
+    def get_from(self) -> JID:
         """Return the value of the stanza's ``'from'`` attribute."""
         return JID(self._get_attr('from'))
 
-    def set_from(self, value):
+    def set_from(self, value: JidStr) -> None:
         """Set the 'from' attribute of the stanza.
 
         :param from: A string or JID object representing the sender's JID.
@@ -1438,11 +1527,11 @@ class StanzaBase(ElementBase):
         """
         return self._set_attr('from', str(value))
 
-    def get_payload(self):
+    def get_payload(self) -> List[ET.Element]:
         """Return a list of XML objects contained in the stanza."""
         return list(self.xml)
 
-    def set_payload(self, value):
+    def set_payload(self, value: Union[List[ElementBase], ElementBase]) -> StanzaBase:
         """Add XML content to the stanza.
 
         :param value: Either an XML or a stanza object, or a list
@@ -1454,12 +1543,12 @@ class StanzaBase(ElementBase):
             self.append(val)
         return self
 
-    def del_payload(self):
+    def del_payload(self) -> StanzaBase:
         """Remove the XML contents of the stanza."""
         self.clear()
         return self
 
-    def reply(self, clear=True):
+    def reply(self, clear: bool = True) -> StanzaBase:
         """Prepare the stanza for sending a reply.
 
         Swaps the ``'from'`` and ``'to'`` attributes.
@@ -1475,7 +1564,7 @@ class StanzaBase(ElementBase):
         new_stanza = copy.copy(self)
         # if it's a component, use from
         if self.stream and hasattr(self.stream, "is_component") and \
-            self.stream.is_component:
+                getattr(self.stream, 'is_component'):
             new_stanza['from'], new_stanza['to'] = self['to'], self['from']
         else:
             new_stanza['to'] = self['from']
@@ -1484,19 +1573,19 @@ class StanzaBase(ElementBase):
             new_stanza.clear()
         return new_stanza
 
-    def error(self):
+    def error(self) -> StanzaBase:
         """Set the stanza's type to ``'error'``."""
         self['type'] = 'error'
         return self
 
-    def unhandled(self):
+    def unhandled(self) -> None:
         """Called if no handlers have been registered to process this stanza.
 
         Meant to be overridden.
         """
         pass
 
-    def exception(self, e):
+    def exception(self, e: Exception) -> None:
         """Handle exceptions raised during stanza processing.
 
         Meant to be overridden.
@@ -1504,18 +1593,21 @@ class StanzaBase(ElementBase):
         log.exception('Error handling {%s}%s stanza', self.namespace,
                                                       self.name)
 
-    def send(self):
+    def send(self) -> None:
         """Queue the stanza to be sent on the XML stream."""
-        self.stream.send(self)
+        if self.stream is not None:
+            self.stream.send(self)
+        else:
+            log.error("Tried to send stanza without a stream: %s", self)
 
-    def __copy__(self):
+    def __copy__(self) -> StanzaBase:
         """Return a copy of the stanza object that does not share the
         same underlying XML object, but does share the same XML stream.
         """
         return self.__class__(xml=copy.deepcopy(self.xml),
                               stream=self.stream)
 
-    def __str__(self, top_level_ns=False):
+    def __str__(self, top_level_ns: bool = False) -> str:
         """Serialize the stanza's XML to a string.
 
         :param bool top_level_ns: Display the top-most namespace.
@@ -1525,27 +1617,3 @@ class StanzaBase(ElementBase):
         return tostring(self.xml, xmlns=xmlns,
                         stream=self.stream,
                         top_level=(self.stream is None))
-
-
-#: A JSON/dictionary version of the XML content exposed through
-#: the stanza interfaces::
-#:
-#:     >>> msg = Message()
-#:     >>> msg.values
-#:    {'body': '', 'from': , 'mucnick': '', 'mucroom': '',
-#:     'to': , 'type': 'normal', 'id': '', 'subject': ''}
-#:
-#: Likewise, assigning to the :attr:`values` will change the XML
-#: content::
-#:
-#:     >>> msg = Message()
-#:     >>> msg.values = {'body': 'Hi!', 'to': 'user@example.com'}
-#:     >>> msg
-#:     '<message to="user@example.com"><body>Hi!</body></message>'
-#:
-#: Child stanzas are exposed as nested dictionaries.
-ElementBase.values = property(ElementBase._get_stanza_values,
-                              ElementBase._set_stanza_values)
-
-ElementBase.get_stanza_values = ElementBase._get_stanza_values
-ElementBase.set_stanza_values = ElementBase._set_stanza_values