code: func ValidateNodeSelector(nodeSelector *core.NodeSelector, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  
  	termFldPath := fldPath.Child("nodeSelectorTerms")
  	if len(nodeSelector.NodeSelectorTerms) == 0 {
  		return append(allErrs, field.Required(termFldPath, "must have at least one node selector term"))
  	}
  
  	for i, term := range nodeSelector.NodeSelectorTerms {
  		allErrs = append(allErrs, ValidateNodeSelectorTerm(term, termFldPath.Index(i))...)
  	}
  
  	return allErrs
  }
docs: // ValidateNodeSelector tests that the specified nodeSelector fields has valid data