code: async def subscribe(self, topic: str):
          
  
          req_msg = {
              'type': 'subscribe',
              'topic': topic,
              'response': True
          }
  
          await self._conn.send_message(req_msg)
docs: Subscribe to a channel
  
          :param topic: required
          :returns: None
  
          Sample ws response
  
          .. code-block:: python
  
              {
                  "type":"message",
                  "topic":"/market/ticker:BTC-USDT",
                  "subject":"trade.ticker",
                  "data":{
                      "sequence":"1545896668986",
                      "bestAsk":"0.08",
                      "size":"0.011",
                      "bestBidSize":"0.036",
                      "price":"0.08",
                      "bestAskSize":"0.18",
                      "bestBid":"0.049"
                  }
              }
  
          Error response
  
          .. code-block:: python
  
              {
                  'code': 404,
                  'data': 'topic /market/ticker:BTC-USDT is not found',
                  'id': '1550868034537',
                  'type': 'error'
              }