diff --git a/slixmpp/features/feature_bind/bind.py b/slixmpp/features/feature_bind/bind.py
index 6c30d9f2..75bbcfa2 100644
--- a/slixmpp/features/feature_bind/bind.py
+++ b/slixmpp/features/feature_bind/bind.py
@@ -1,4 +1,3 @@
-
 # Slixmpp: The Slick XMPP Library
 # Copyright (C) 2011  Nathanael C. Fritz
 # This file is part of Slixmpp.
@@ -11,6 +10,7 @@ from slixmpp.stanza import Iq, StreamFeatures
 from slixmpp.features.feature_bind import stanza
 from slixmpp.xmlstream import register_stanza_plugin
 from slixmpp.plugins import BasePlugin
+from typing import ClassVar, Set
 
 
 log = logging.getLogger(__name__)
@@ -20,7 +20,7 @@ class FeatureBind(BasePlugin):
 
     name = 'feature_bind'
     description = 'RFC 6120: Stream Feature: Resource Binding'
-    dependencies = set()
+    dependencies: ClassVar[Set[str]] = set()
     stanza = stanza
 
     def plugin_init(self):
diff --git a/slixmpp/features/feature_mechanisms/mechanisms.py b/slixmpp/features/feature_mechanisms/mechanisms.py
index dfdca010..db2d73d0 100644
--- a/slixmpp/features/feature_mechanisms/mechanisms.py
+++ b/slixmpp/features/feature_mechanisms/mechanisms.py
@@ -1,4 +1,3 @@
-
 # Slixmpp: The Slick XMPP Library
 # Copyright (C) 2011  Nathanael C. Fritz
 # This file is part of Slixmpp.
@@ -15,6 +14,8 @@ from slixmpp.xmlstream.matcher import MatchXPath
 from slixmpp.xmlstream.handler import Callback
 from slixmpp.features.feature_mechanisms import stanza
 
+from typing import ClassVar, Set
+
 
 log = logging.getLogger(__name__)
 
@@ -23,7 +24,7 @@ class FeatureMechanisms(BasePlugin):
 
     name = 'feature_mechanisms'
     description = 'RFC 6120: Stream Feature: SASL'
-    dependencies = set()
+    dependencies: ClassVar[Set[str]] = set()
     stanza = stanza
     default_config = {
         'use_mech': None,
diff --git a/slixmpp/features/feature_mechanisms/stanza/abort.py b/slixmpp/features/feature_mechanisms/stanza/abort.py
index afa75cde..a430fa0f 100644
--- a/slixmpp/features/feature_mechanisms/stanza/abort.py
+++ b/slixmpp/features/feature_mechanisms/stanza/abort.py
@@ -1,9 +1,9 @@
-
 # Slixmpp: The Slick XMPP Library
 # Copyright (C) 2011  Nathanael C. Fritz
 # This file is part of Slixmpp.
 # See the file LICENSE for copying permission.
 from slixmpp.xmlstream import StanzaBase
+from typing import ClassVar, Set
 
 
 class Abort(StanzaBase):
@@ -13,7 +13,7 @@ class Abort(StanzaBase):
 
     name = 'abort'
     namespace = 'urn:ietf:params:xml:ns:xmpp-sasl'
-    interfaces = set()
+    interfaces: ClassVar[Set[str]] = set()
     plugin_attrib = name
 
     def setup(self, xml):
diff --git a/slixmpp/features/feature_preapproval/preapproval.py b/slixmpp/features/feature_preapproval/preapproval.py
index 5dceeb06..46fbaeec 100644
--- a/slixmpp/features/feature_preapproval/preapproval.py
+++ b/slixmpp/features/feature_preapproval/preapproval.py
@@ -1,4 +1,3 @@
-
 # Slixmpp: The Slick XMPP Library
 # Copyright (C) 2012  Nathanael C. Fritz
 # This file is part of Slixmpp.
@@ -9,6 +8,7 @@ from slixmpp.stanza import StreamFeatures
 from slixmpp.features.feature_preapproval import stanza
 from slixmpp.xmlstream import register_stanza_plugin
 from slixmpp.plugins.base import BasePlugin
+from typing import ClassVar, Set
 
 
 log = logging.getLogger(__name__)
@@ -18,7 +18,7 @@ class FeaturePreApproval(BasePlugin):
 
     name = 'feature_preapproval'
     description = 'RFC 6121: Stream Feature: Subscription Pre-Approval'
-    dependences = set()
+    dependencies: ClassVar[Set[str]] = set()
     stanza = stanza
 
     def plugin_init(self):
diff --git a/slixmpp/features/feature_preapproval/stanza.py b/slixmpp/features/feature_preapproval/stanza.py
index b5d68f8e..630a0b7e 100644
--- a/slixmpp/features/feature_preapproval/stanza.py
+++ b/slixmpp/features/feature_preapproval/stanza.py
@@ -1,14 +1,14 @@
-
 # Slixmpp: The Slick XMPP Library
 # Copyright (C) 2012  Nathanael C. Fritz
 # This file is part of Slixmpp.
 # See the file LICENSE for copying permission.
 from slixmpp.xmlstream import ElementBase
+from typing import ClassVar, Set
 
 
 class PreApproval(ElementBase):
 
     name = 'sub'
     namespace = 'urn:xmpp:features:pre-approval'
-    interfaces = set()
+    interfaces: ClassVar[Set[str]] = set()
     plugin_attrib = 'preapproval'
diff --git a/slixmpp/features/feature_rosterver/rosterver.py b/slixmpp/features/feature_rosterver/rosterver.py
index ae980388..1dea6878 100644
--- a/slixmpp/features/feature_rosterver/rosterver.py
+++ b/slixmpp/features/feature_rosterver/rosterver.py
@@ -1,4 +1,3 @@
-
 # Slixmpp: The Slick XMPP Library
 # Copyright (C) 2012  Nathanael C. Fritz
 # This file is part of Slixmpp.
@@ -9,6 +8,7 @@ from slixmpp.stanza import StreamFeatures
 from slixmpp.features.feature_rosterver import stanza
 from slixmpp.xmlstream import register_stanza_plugin
 from slixmpp.plugins.base import BasePlugin
+from typing import ClassVar, Set
 
 
 log = logging.getLogger(__name__)
@@ -18,7 +18,7 @@ class FeatureRosterVer(BasePlugin):
 
     name = 'feature_rosterver'
     description = 'RFC 6121: Stream Feature: Roster Versioning'
-    dependences = set()
+    dependences: ClassVar[Set[str]] = set()
     stanza = stanza
 
     def plugin_init(self):
diff --git a/slixmpp/features/feature_rosterver/stanza.py b/slixmpp/features/feature_rosterver/stanza.py
index 3696d89a..428dbb26 100644
--- a/slixmpp/features/feature_rosterver/stanza.py
+++ b/slixmpp/features/feature_rosterver/stanza.py
@@ -1,14 +1,14 @@
-
 # Slixmpp: The Slick XMPP Library
 # Copyright (C) 2012  Nathanael C. Fritz
 # This file is part of Slixmpp.
 # See the file LICENSE for copying permission.
 from slixmpp.xmlstream import ElementBase
+from typing import Set, ClassVar
 
 
 class RosterVer(ElementBase):
 
     name = 'ver'
     namespace = 'urn:xmpp:features:rosterver'
-    interfaces = set()
+    interfaces: ClassVar[Set[str]] = set()
     plugin_attrib = 'rosterver'
diff --git a/slixmpp/features/feature_session/session.py b/slixmpp/features/feature_session/session.py
index 0f9b9dd7..83e6c220 100644
--- a/slixmpp/features/feature_session/session.py
+++ b/slixmpp/features/feature_session/session.py
@@ -11,6 +11,7 @@ from slixmpp.xmlstream import register_stanza_plugin
 from slixmpp.plugins import BasePlugin
 
 from slixmpp.features.feature_session import stanza
+from typing import  ClassVar, Set
 
 
 log = logging.getLogger(__name__)
@@ -20,7 +21,7 @@ class FeatureSession(BasePlugin):
 
     name = 'feature_session'
     description = 'RFC 3920: Stream Feature: Start Session'
-    dependencies = set()
+    dependencies: ClassVar[Set[str]] = set()
     stanza = stanza
 
     def plugin_init(self):
diff --git a/slixmpp/features/feature_starttls/stanza.py b/slixmpp/features/feature_starttls/stanza.py
index 2f971723..70979402 100644
--- a/slixmpp/features/feature_starttls/stanza.py
+++ b/slixmpp/features/feature_starttls/stanza.py
@@ -4,39 +4,47 @@
 # This file is part of Slixmpp.
 # See the file LICENSE for copying permission.
 from slixmpp.xmlstream import StanzaBase, ElementBase
+from typing import Set, ClassVar
 
 
 class STARTTLS(StanzaBase):
-
-    """
     """
 
+    .. code-block:: xml
+
+         <starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
+
+    """
     name = 'starttls'
     namespace = 'urn:ietf:params:xml:ns:xmpp-tls'
     interfaces = {'required'}
     plugin_attrib = name
 
     def get_required(self):
-        """
-        """
         return True
 
 
 class Proceed(StanzaBase):
-
-    """
     """
 
+    .. code-block:: xml
+
+        <proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
+
+    """
     name = 'proceed'
     namespace = 'urn:ietf:params:xml:ns:xmpp-tls'
-    interfaces = set()
+    interfaces: ClassVar[Set[str]] = set()
 
 
 class Failure(StanzaBase):
-
-    """
     """
 
+    .. code-block:: xml
+
+        <failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
+
+    """
     name = 'failure'
     namespace = 'urn:ietf:params:xml:ns:xmpp-tls'
-    interfaces = set()
+    interfaces: ClassVar[Set[str]] = set()
diff --git a/slixmpp/features/feature_starttls/starttls.py b/slixmpp/features/feature_starttls/starttls.py
index 89cbb6b2..318d4a5e 100644
--- a/slixmpp/features/feature_starttls/starttls.py
+++ b/slixmpp/features/feature_starttls/starttls.py
@@ -12,6 +12,8 @@ from slixmpp.xmlstream.matcher import MatchXPath
 from slixmpp.xmlstream.handler import CoroutineCallback
 from slixmpp.features.feature_starttls import stanza
 
+from typing import ClassVar, Set
+
 
 log = logging.getLogger(__name__)
 
@@ -20,7 +22,7 @@ class FeatureSTARTTLS(BasePlugin):
 
     name = 'feature_starttls'
     description = 'RFC 6120: Stream Feature: STARTTLS'
-    dependencies = set()
+    dependencies: ClassVar[Set[str]] = set()
     stanza = stanza
 
     def plugin_init(self):