code: def start(self):
          
          if self.running:
              raise RuntimeError("client already running")
  
          self._main_task = asyncio.ensure_future(
              self._main(),
              loop=self._loop
          )
          self._main_task.add_done_callback(self._on_main_done)
docs: Start the client. If it is already :attr:`running`,
          :class:`RuntimeError` is raised.
  
          While the client is running, it will try to keep an XMPP connection
          open to the server associated with :attr:`local_jid`.