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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 _rpartition(entity, sep):
 """Python2.4 doesn't have an rpartition method so we provide our own that mimics str.rpartition from later releases. Split the string at the last occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing two empty strings, followed by the string itself. """

    idx = entity.rfind(sep)
    if idx == -1:
        return '', '', entity
    return entity[:idx], sep, entity[idx + 1:]