code: def send(self, xso):
          
          with self._writer.buffer():
              xso.unparse_to_sax(self._writer)
docs: Send a single XML stream object.
  
          :param xso: Object to serialise and send.
          :type xso: :class:`aioxmpp.xso.XSO`
          :raises Exception: from any serialisation errors, usually
                             :class:`ValueError`.
  
          Serialise the `xso` and send it over the stream. If any serialisation
          error occurs, no data is sent over the stream and the exception is
          re-raised; the :meth:`send` method thus provides strong exception
          safety.
  
          .. warning::
  
             The behaviour of :meth:`send` after :meth:`abort` or :meth:`close`
             and before :meth:`start` is undefined.