Updated the XEP-0085 plugin.

Can now be used as so:

>>> msg['chat_state']
''
>>> msg
<message />

>>> msg['chat_state'] = 'paused'
>>> msg
<message>
  <paused xmlns="http://jabber.org/protocol/chatstates" />
</message>

>>> msg['chat_state']
'paused'

>>> del msg['chat_state']
>>> msg
<message />

sleekxmpp/plugins/xep_0085/stanza.py

@@ -0,0 +1,73 @@
+"""
+    SleekXMPP: The Sleek XMPP Library
+    Copyright (C) 2011 Nathanael C. Fritz, Lance J.T. Stout
+    This file is part of SleekXMPP.
+
+    See the file LICENSE for copying permissio
+"""
+
+import sleekxmpp
+from sleekxmpp.xmlstream import ElementBase, ET
+
+
+class ChatState(ElementBase):
+
+    """
+    Example chat state stanzas:
+        <message>
+          <active xmlns="http://jabber.org/protocol/chatstates" />
+        </message>
+
+        <message>
+          <paused xmlns="http://jabber.org/protocol/chatstates" />
+        </message>
+
+    Stanza Interfaces:
+        chat_state
+
+    Attributes:
+        states
+
+    Methods:
+        get_chat_state
+        set_chat_state
+        del_chat_state
+    """
+
+    name = ''
+    namespace = 'http://jabber.org/protocol/chatstates'
+    plugin_attrib = 'chat_state'
+    interfaces = set(('chat_state',))
+    is_extension = True
+
+    states = set(('active', 'composing', 'gone', 'inactive', 'paused'))
+
+    def setup(self, xml=None):
+        self.xml = ET.Element('')
+        return True
+
+    def get_chat_state(self):
+        parent = self.parent()
+        for state in self.states:
+            state_xml = parent.find('{%s}%s' % (self.namespace, state))
+            if state_xml is not None:
+                self.xml = state_xml
+                return state
+        return ''
+
+    def set_chat_state(self, state):
+        self.del_chat_state()
+        parent = self.parent()
+        if state in self.states:
+            self.xml = ET.Element('{%s}%s' % (self.namespace, state))
+            parent.append(self.xml)
+        elif state not in [None, '']:
+            raise ValueError('Invalid chat state')
+
+    def del_chat_state(self):
+        parent = self.parent()
+        for state in self.states:
+            state_xml = parent.find('{%s}%s' % (self.namespace, state))
+            if state_xml is not None:
+                self.xml = ET.Element('')
+                parent.xml.remove(state_xml)