docs: public void addPackageFromDrl(final Reader reader,
                                    final Resource sourceResource) throws DroolsParserException,
              IOException {
          this.resource = sourceResource;
          final DrlParser parser = new DrlParser(configuration.getLanguageLevel());
          final PackageDescr pkg = parser.parse(sourceResource, reader);
          this.results.addAll(parser.getErrors());
          if (pkg == null) {
              addBuilderResult(new ParserError(sourceResource, "Parser returned a null Package", 0, 0));
          }
  
          if (!parser.hasErrors()) {
              addPackage(pkg);
          }
          this.resource = null;
      }