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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 _last_bookmark(b0, b1):
 """ Return the latest of two bookmarks by looking for the maximum integer value following the last colon in the bookmark string. """

    n = [None, None]
    _, _, n[0] = b0.rpartition(":")
    _, _, n[1] = b1.rpartition(":")
    for i in range(2):
        try:
            n[i] = int(n[i])
        except ValueError:
            raise ValueError("Invalid bookmark: {}".format(b0))
    return b0 if n[0] > n[1] else b1