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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 _parse_ranking(self, field, boxscore):
 """ Parse each team's rank if applicable. Retrieve the team's rank according to the rankings published each week. The ranking for the week is only located in the scores section at the top of the page and not in the actual boxscore information. The rank is after the team name inside a parenthesis with a special 'pollrank' attribute. If this is not in the team's boxscore information, the team is assumed to not have a rank and will return a value of None. Parameters field : string The name of the attribute to parse. boxscore : PyQuery object A PyQuery obejct containing all of the HTML data from the boxscore. Returns ------- int An int representing the team's ranking or None if the team is not ranked. """

        ranking = None
        index = BOXSCORE_ELEMENT_INDEX[field]
        teams_boxscore = boxscore(BOXSCORE_SCHEME[field])
        # Occasionally, the list of boxscores for the day won't be saved on the
        # page. If that's the case, return the default ranking.
        if str(teams_boxscore) == '':
            return ranking
        team = pq(teams_boxscore[index])
        if 'pollrank' in str(team):
            rank_str = re.findall(r'\(\d+\)', str(team))
            if len(rank_str) == 1:
                ranking = int(rank_str[0].replace('(', '').replace(')', ''))
        return ranking