code: func (s *CombinedPrimitiveSlice) lookup(l interface{}) *PrimitiveListItem {
  	val := fmt.Sprintf("%v", l)
  	for _, i := range s.Items {
  		if fmt.Sprintf("%v", i.Value) == val {
  			return i
  		}
  	}
  	return nil
  }
docs: // Contains returns true if the slice contains the l