def insert_duplicate_kanji(kanji_string):
    """
    Inserts full kanji for characters where a shorthand is used.

        >>> k = insert_duplicate_kanji(u'私々')
        >>> expected = u'私私'
        >>> k == expected
        True
    """
    loc = kanji_string.find('々')
    while loc > 0:
        dup = kanji_string[loc - 1]
        kanji_string = kanji_string[:loc] + dup + kanji_string[loc + 1:]
        loc = kanji_string.find('々')
    return kanji_string
