code: def _ensure_channel_connected(self, destination_id):
          
          if destination_id not in self._open_channels:
              self._open_channels.append(destination_id)
  
              self.send_message(
                  destination_id, NS_CONNECTION,
                  {MESSAGE_TYPE: TYPE_CONNECT,
                   'origin': {},
                   'userAgent': 'PyChromecast',
                   'senderInfo': {
                       'sdkType': 2,
                       'version': '15.605.1.3',
                       'browserVersion': "44.0.2403.30",
                       'platform': 4,
                       'systemVersion': 'Macintosh; Intel Mac OS X10_10_3',
                       'connectionType': 1}},
                  no_add_request_id=True)
docs: Ensure we opened a channel to destination_id.