code: func NewStackConverter(version string) (StackConverter, error) {
  	switch version {
  	case "v1beta1":
  		return stackV1Beta1Converter{}, nil
  	case "v1beta2":
  		return stackV1Beta2Converter{}, nil
  	case "v1alpha3":
  		return stackV1Alpha3Converter{}, nil
  	default:
  		return nil, errors.Errorf("stack version %s unsupported", version)
  	}
  }
docs: // NewStackConverter returns a converter from types.Config (compose) to the specified
  // stack version or error out if the version is not supported or existent.