Add ability for a user to get retrieve subscriptions, with tests.

sleekxmpp/plugins/xep_0060/pubsub.py

@@ -171,6 +171,12 @@ class xep_0060(base_plugin):
         iq['pubsub']['unsubscribe']['subid'] = subid
         return iq.send(block=block, callback=callback, timeout=timeout)
 
+    def get_subscriptions(self, jid, node=None, ifrom=None, block=True,
+                          callback=None, timeout=None):
+        iq = self.xmpp.Iq(sto=jid, sfrom=ifrom, stype='get')
+        iq['pubsub']['subscriptions']['node'] = node
+        return iq.send(block=block, callback=callback, timeout=timeout)
+
     def get_subscription_options(self, jid, node, user_jid, ifrom=None,
                                  block=True, callback=None, timeout=None):
         iq = self.xmpp.Iq(sto=jid, sfrom=ifrom, stype='get')

sleekxmpp/plugins/xep_0060/stanza/pubsub.py

@@ -65,7 +65,7 @@ class Subscriptions(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'subscriptions'
     plugin_attrib = 'subscriptions'
-    interfaces = set(tuple())
+    interfaces = set(('node',))
     plugin_attrib_map = {}
     plugin_tag_map = {}
     subitem = (Subscription,)