code: def flush(self):
          # type: () -> None
          
          if self._closed:
              raise IOError('tried to flush closed connection')
          assert self._parentout is not None
          self._parentout.flush()
docs: Flush the channel to FORM.
  
          Flush the communication channel to FORM. Because :meth:`write` is
          buffered and :meth:`read` is a blocking operation, this method is used
          for asynchronous execution of FORM scripts.