code: func ValidateRuntimeClassUpdate(new, old *node.RuntimeClass) field.ErrorList {
  	allErrs := apivalidation.ValidateObjectMetaUpdate(&new.ObjectMeta, &old.ObjectMeta, field.NewPath("metadata"))
  
  	allErrs = append(allErrs, apivalidation.ValidateImmutableField(new.Handler, old.Handler, field.NewPath("handler"))...)
  
  	return allErrs
  }
docs: // ValidateRuntimeClassUpdate validates an update to the object