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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_MML(self, mml):
        ''' parse the MML structure '''
        hashes_c = []
        mentions_c = []
        soup = BeautifulSoup(mml, "lxml")
        hashes = soup.find_all('hash', {"tag": True})
        for hashe in hashes:
            hashes_c.append(hashe['tag'])
        mentions = soup.find_all('mention', {"uid": True})
        for mention in mentions:
            mentions_c.append(mention['uid'])
        msg_string = soup.messageml.text.strip()
        self.logger.debug('%s : %s : %s' % (hashes_c, mentions_c, msg_string))
        return hashes_c, mentions_c, msg_string