code: async def pong(self, data: bytes = b"") -> None:
          
          await self.ensure_open()
  
          data = encode_data(data)
  
          await self.write_frame(True, OP_PONG, data)
docs: This coroutine sends a pong.
  
          An unsolicited pong may serve as a unidirectional heartbeat.
  
          The content may be overridden with the optional ``data`` argument
          which must be a string (which will be encoded to UTF-8) or a
          bytes-like object.