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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 is_slug(string, sign='-'):
 """ Checks if a given string is a slug. :param string: String to check. :type string: str :param sign: Join sign used by the slug. :type sign: str :return: True if slug, false otherwise. """

    if not is_full_string(string):
        return False
    rex = r'^([a-z\d]+' + re.escape(sign) + r'?)*[a-z\d]$'
    return re.match(rex, string) is not None