Decode string encoded by `unicode_string`

def decode_unicode_string(string):
    """
    Decode string encoded by `unicode_string`
    """
    if string.startswith('[BASE64-DATA]') and string.endswith('[/BASE64-DATA]'):
        return base64.b64decode(string[len('[BASE64-DATA]'):-len('[/BASE64-DATA]')])
    return string