code: func (s *Scheme) ObjectKind(obj Object) (unversioned.GroupVersionKind, error) {
  	gvks, err := s.ObjectKinds(obj)
  	if err != nil {
  		return unversioned.GroupVersionKind{}, err
  	}
  	return gvks[0], nil
  }
docs: // ObjectKind returns the group,version,kind of the go object,
  // or an error if it's not a pointer or is unregistered.