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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 os_is_running(pid):
    '''
    Use OS facilities to determine if a process is running
    '''
    if isinstance(pid, six.string_types):
        pid = int(pid)
    if HAS_PSUTIL:
        return psutil.pid_exists(pid)
    else:
        try:
            os.kill(pid, 0)  # SIG 0 is the "are you alive?" signal
            return True
        except OSError:
            return False