code: func validateVolumeBindingMode(mode *storage.VolumeBindingMode, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  	if mode == nil {
  		allErrs = append(allErrs, field.Required(fldPath, ""))
  	} else if !supportedVolumeBindingModes.Has(string(*mode)) {
  		allErrs = append(allErrs, field.NotSupported(fldPath, mode, supportedVolumeBindingModes.List()))
  	}
  
  	return allErrs
  }
docs: // validateVolumeBindingMode tests that VolumeBindingMode specifies valid values.