code: func ValidatePositiveQuantity(value resource.Quantity, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  	if value.Cmp(resource.Quantity{}) < 0 {
  		allErrs = append(allErrs, field.Invalid(fldPath, value.String(), isNegativeErrorMsg))
  	}
  	return allErrs
  }
docs: // Validates that a Quantity is not negative