docs: private BaseDescr lhsParen(CEDescrBuilder<?, ?> ce,
              boolean allowOr) throws RecognitionException {
          match(input,
                  DRL6Lexer.LEFT_PAREN,
                  null,
                  null,
                  DroolsEditorType.SYMBOL);
          if (state.failed)
              return null;
  
          if (state.backtracking == 0 && input.LA(1) != DRL6Lexer.EOF) {
              helper.emit(Location.LOCATION_LHS_BEGIN_OF_CONDITION);
          }
          BaseDescr descr = lhsOr(ce,
                  allowOr);
          if (state.failed)
              return null;
  
          match(input,
                  DRL6Lexer.RIGHT_PAREN,
                  null,
                  null,
                  DroolsEditorType.SYMBOL);
          if (state.failed)
              return null;
  
          return descr;
      }