code: def send_message(self, data, inc_session_id=False,
                       callback_function=None):
          
          self._check_registered()
  
          if not self.target_platform and \
             self.namespace not in self._socket_client.app_namespaces:
              if self.supporting_app_id is not None:
                  self.launch()
  
              else:
                  raise UnsupportedNamespace(
                      ("Namespace {} is not supported by running"
                       "application.").format(self.namespace))
  
          return self._message_func(
              self.namespace, data, inc_session_id, callback_function)
docs: Send a message on this namespace to the Chromecast.
  
          Will raise a NotConnected exception if not connected.