docs: public void traverseModels( File sourceDirectory, ReportModelFileHandler handler ) {
          for( ReportModelFile f : Files.fileTreeTraverser().breadthFirstTraversal( sourceDirectory )
              .filter( FilePredicates.endsWith( ".json" ) )
              .transform( new ReportModelFileReader() ) ) {
              handler.handleReportModel( f );
          }
      }