code: func NestedMap(obj map[string]interface{}, fields ...string) (map[string]interface{}, bool, error) {
  	m, found, err := nestedMapNoCopy(obj, fields...)
  	if !found || err != nil {
  		return nil, found, err
  	}
  	return runtime.DeepCopyJSON(m), true, nil
  }
docs: // NestedMap returns a deep copy of map[string]interface{} value of a nested field.
  // Returns false if value is not found and an error if not a map[string]interface{}.