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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 _newer(a, b):
 """Inquire whether file a was written since file b."""

    if not os.path.exists(a):
        return False
    if not os.path.exists(b):
        return True
    return os.path.getmtime(a) >= os.path.getmtime(b)