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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 cache_get(cache_dir, cache_key, default=None):
 """ Returns the content of a cache item or the given default """

    filename = os.path.join(cache_dir, cache_key)

    if os.path.isfile(filename):
        with open(filename, 'r') as f:
            return f.read()

    return default