code: func validateVolumeAttachmentSpec(
  	spec *storage.VolumeAttachmentSpec, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  	allErrs = append(allErrs, validateAttacher(spec.Attacher, fldPath.Child("attacher"))...)
  	allErrs = append(allErrs, validateVolumeAttachmentSource(&spec.Source, fldPath.Child("source"))...)
  	allErrs = append(allErrs, validateNodeName(spec.NodeName, fldPath.Child("nodeName"))...)
  	return allErrs
  }
docs: // ValidateVolumeAttachmentSpec tests that the specified VolumeAttachmentSpec
  // has valid data.