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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def restart(self, subthread=None):
 """Restarts the loop function Tries to restart the loop thread using the current thread. Raises RuntimeError if a previous call to Loop.start was not made. :param subthread: True/False value used when calling Loop.start(subthread=subthread). If set to None it uses the same value as the last call to Loop.start. """

        if self._in_subthread is None:
            raise RuntimeError('A call to start must first be placed before restart')
        self.stop(silent=True)
        if subthread is None:
            subthread = self._in_subthread
        self.__init__(self.target, self.args, self.kwargs, self.on_stop)
        self.start(subthread=subthread)