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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 get(cache_dir=CACHE_DIR):
 """Get the current wallpaper."""

    current_wall = os.path.join(cache_dir, "wal")

    if os.path.isfile(current_wall):
        return util.read_file(current_wall)[0]

    return "None"