code: def build_reply_opts(self, message):
          
          try:
              source = message['metadata']['source_channel']
              thread = message['metadata'].get('thread_ts')
              opts = {'target': source, 'thread': thread}
          except LookupError:
              source = None
              opts = None
              logger.error("Could not identify source from  message:{}\n"
                           .format(str(message)))
          return opts
docs: Convenience method for constructing default options for a
          reply message.
  
          :param message: the message to reply to
          :return: opts