code: def make_stream_features(self, stream, features):
          
          self.stream = stream
          if stream.peer_authenticated and not stream.peer.resource:
              ElementTree.SubElement(features, FEATURE_BIND)
docs: Add resource binding feature to the <features/> element of the
          stream.
  
          [receving entity only]
  
          :returns: update <features/> element.