code: func (r *SearchRequest) DocValueFieldWithFormat(field DocvalueField) *SearchRequest {
  	r.searchSource = r.searchSource.DocvalueFieldWithFormat(field)
  	return r
  }
docs: // DocValueFieldWithFormat adds a docvalue based field to load and return.
  // The field does not have to be stored, but it's recommended to use
  // non analyzed or numeric fields.