code: def list_favorites(current):
      
      current.output = {'status': 'OK', 'code': 200, 'favorites': []}
      query_set = Favorite(current).objects.filter(user_id=current.user_id)
      if current.input['channel_key']:
          query_set = query_set.filter(channel_id=current.input['channel_key'])
      current.output['favorites'] = [{
                                         'key': fav.key,
                                         'channel_key': fav.channel.key,
                                         'message_key': fav.message.key,
                                         'message_summary': fav.summary,
                                         'channel_name': fav.channel_name
                                     } for fav in query_set]
docs: List user's favorites. If "channel_key" given, will return favorites belong to that channel.
  
      .. code-block:: python
  
          #  request:
              {
              'view':'_zops_list_favorites,
              'channel_key': key,
              }
  
          #  response:
              {
              'status': 'OK',
              'code': 200
              'favorites':[{'key': key,
                          'channel_key': key,
                          'message_key': key,
                          'message_summary': string, # max 60 char
                          'channel_name': string,
                          },]
              }