code: func (s *SliceQuery) Source() (interface{}, error) {
  	m := make(map[string]interface{})
  	if s.field != "" {
  		m["field"] = s.field
  	}
  	if s.id != nil {
  		m["id"] = *s.id
  	}
  	if s.max != nil {
  		m["max"] = *s.max
  	}
  	return m, nil
  }
docs: // Source returns the JSON body.