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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 down(self, down_uid):
        '''
        Download the entity by UID.
        '''
        down_url = MPost.get_by_uid(down_uid).extinfo.get('tag__file_download', '')
        print('=' * 40)
        print(down_url)
        str_down_url = str(down_url)[15:]


        if down_url:
            ment_id = MEntity.get_id_by_impath(str_down_url)
            if ment_id:
                MEntity2User.create_entity2user(ment_id, self.userinfo.uid)
            return True
        else:
            return False