code: def set_header_s(self, stream):
          
  
          if self.argstreams[1].state == StreamState.init:
              self.argstreams[1] = stream
          else:
              raise TChannelError(
                  "Unable to change the header since the streaming has started")
docs: Set customized header stream.
  
          Note: the header stream can only be changed before the stream
          is consumed.
  
          :param stream: InMemStream/PipeStream for header
  
          :except TChannelError:
              Raise TChannelError if the stream is being sent when you try
              to change the stream.