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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 _is_pid_running_on_unix(pid):
 """ Check if PID is running for Unix systems. """

    try:
        os.kill(pid, 0)
    except OSError as err:
        # if error is ESRCH, it means the process doesn't exist
        return not err.errno == os.errno.ESRCH
    return True