code: async def start(self):
          
  
          if self._server_task is not None:
              self._logger.debug("AsyncValidatingWSServer.start() called twice, ignoring")
              return
  
          started_signal = self._loop.create_future()
          self._server_task = self._loop.add_task(self._run_server_task(started_signal))
  
          await started_signal
  
          if self.port is None:
              self.port = started_signal.result()
docs: Start the websocket server.
  
          When this method returns, the websocket server will be running and
          the port property of this class will have its assigned port number.
  
          This method should be called only once in the lifetime of the server
          and must be paired with a call to stop() to cleanly release the
          server's resources.