docs: public static void main(String[] args) {
      Treebank treebank = new DiskTreebank();
      CategoryWordTag.suppressTerminalDetails = true;
      treebank.loadPath(args[0]);
      final HeadFinder chf = new CollinsHeadFinder();
      treebank.apply(new TreeVisitor() {
        public void visitTree(Tree pt) {
          pt.percolateHeads(chf);
          pt.pennPrint();
          System.out.println();
        }
      });
    }