code: func (m *DbMap) SelectNullStr(query string, args ...interface{}) (sql.NullString, error) {
  	if m.ExpandSliceArgs {
  		expandSliceArgs(&query, args...)
  	}
  
  	return SelectNullStr(m, query, args...)
  }
docs: // SelectNullStr is a convenience wrapper around the gorp.SelectNullStr function