docs: def raw_message_to(self, token, message):
          """Convert message to JSON and send it to the client with token"""
          if token not in self._clients:
              log.critical("Client with token '{0}' not found!".format(token))
              return
          client = self._clients[token]
          try:
              client.write_message(message)
          except (AttributeError, tornado.websocket.WebSocketClosedError):
              log.error("Lost connection to client '{0}'".format(client))
          else:
              print("Sent {0} bytes.".format(len(message)))