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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 kill(self, wait=True, sig=None):
 """ Kill the process if running. :param bool wait: set to `True` to wait for the process to end, or False, to simply proceed after sending signal. :param int sig: signal used to kill process run by the executor. None by default. :returns: itself :rtype: SimpleExecutor """

        if sig is None:
            sig = self._sig_kill
        if self.running():
            os.killpg(self.process.pid, sig)
            if wait:
                self.process.wait()

        self._kill_all_kids(sig)
        self._clear_process()
        return self