code: func validateAttacher(attacher string, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  	if len(attacher) == 0 {
  		allErrs = append(allErrs, field.Required(fldPath, attacher))
  	}
  	return allErrs
  }
docs: // validateAttacher tests if attacher is a valid qualified name.