<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def send_stop_signal(self, silent=False):
 """Sends a stop signal to the loop thread :param silent: True/False value that specifies whether or not to raise RuntimeError if the loop is currently not running :return: """

        if self.is_running():
            self._stop_signal = True
        elif not silent:
            raise RuntimeError('Loop is currently not running')