code: func ValidatePriorityClassUpdate(pc, oldPc *scheduling.PriorityClass) field.ErrorList {
  	allErrs := apivalidation.ValidateObjectMetaUpdate(&pc.ObjectMeta, &oldPc.ObjectMeta, field.NewPath("metadata"))
  	// Name is immutable and is checked by the ObjectMeta validator.
  	if pc.Value != oldPc.Value {
  		allErrs = append(allErrs, field.Forbidden(field.NewPath("Value"), "may not be changed in an update."))
  	}
  	return allErrs
  }
docs: // ValidatePriorityClassUpdate tests if required fields in the PriorityClass are
  // set and are valid. PriorityClass does not allow updating Name, and Value.