code: func (cli *Client) NewVersionError(APIrequired, feature string) error {
  	if cli.version != "" && versions.LessThan(cli.version, APIrequired) {
  		return fmt.Errorf("%q requires API version %s, but the Docker daemon API version is %s", feature, APIrequired, cli.version)
  	}
  	return nil
  }
docs: // NewVersionError returns an error if the APIVersion required
  // if less than the current supported version