private static DiskTreebank makeSecondaryTreebank(String treebankPath, Options op, FileFilter filt) {
    System.err.println("Additionally training using secondary disk treebank: " + treebankPath + ' ' + filt);
    DiskTreebank trainTreebank = op.tlpParams.diskTreebank();
    if (filt == null) {
      trainTreebank.loadPath(treebankPath);
    } else {
      trainTreebank.loadPath(treebankPath, filt);
    }
    return trainTreebank;
  }