code: func (qp *QueryParserBase) Parse(query string) (res search.Query, err error) {
  	qp.spi.ReInit(newFastCharStream(strings.NewReader(query)))
  	if res, err = qp.spi.TopLevelQuery(qp.field); err != nil {
  		return nil, errors.New(fmt.Sprintf("Cannot parse '%v': %v", query, err))
  	}
  	if res != nil {
  		return res, nil
  	}
  	return qp.newBooleanQuery(false), nil
  }
docs: // L116