docs: def validate_unicode_decode_error_handler(dummy, value):
      """Validate the Unicode decode error handler option of CodecOptions.
      """
      if value not in _UNICODE_DECODE_ERROR_HANDLERS:
          raise ValueError("%s is an invalid Unicode decode error handler. "
                           "Must be one of "
                           "%s" % (value, tuple(_UNICODE_DECODE_ERROR_HANDLERS)))
      return value