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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 update_label(signature, post_data):
    '''
    Update the label when updating.
    '''
    current_tag_infos = MPost2Label.get_by_uid(signature).objects()
    if 'tags' in post_data:
        pass
    else:
        return False

    tags_arr = [x.strip() for x in post_data['tags'].split(',')]
    for tag_name in tags_arr:
        if tag_name == '':
            pass
        else:
            MPost2Label.add_record(signature, tag_name, 1)

    for cur_info in current_tag_infos:
        if cur_info.tag_name in tags_arr:
            pass
        else:
            MPost2Label.remove_relation(signature, cur_info.tag_id)