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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_newer(source, target):
 """Return true if 'source' exists and is more recently modified than 'target', or if 'source' exists and 'target' doesn't. Return false if both exist and 'target' is the same age or younger than 'source'. Raise ValueError if 'source' does not exist. """

    if not os.path.exists(source):
        raise ValueError("file '%s' does not exist" % source)
    if not os.path.exists(target):
        return 1

    from stat import ST_MTIME
    mtime1 = os.stat(source)[ST_MTIME]
    mtime2 = os.stat(target)[ST_MTIME]

    return mtime1 > mtime2