code: public <T extends StateVisitor> T visitInPreOrder(T v, int node) {
      visitInPreOrder(v, node, new BitSet());
      return v;
    }
docs: Visits all states in preorder. Returning false from
  {@link StateVisitor#accept(int)} skips traversal of all sub-states of a
  given state.
  
  @param v Visitor to receive traversal calls.
  @param <T> A subclass of {@link StateVisitor}.
  @param node Identifier of the node.
  @return Returns the argument (for access to anonymous class fields).