code: func (s *SearchSource) StoredField(storedFieldName string) *SearchSource {
  	s.storedFieldNames = append(s.storedFieldNames, storedFieldName)
  	return s
  }
docs: // StoredField adds a single field to load and return (note, must be stored) as
  // part of the search request. If none are specified, the source of the
  // document will be returned.