adler99

 // create note & commitment
  let note = to
      .create_note(value, Fs::random(&mut rng), &JUBJUB)
      .unwrap();
  let cm = Node::new(note.cm(&JUBJUB).into_repr());

  // create empty commitment tree and add commitment
  let mut tree = CommitmentTree::new();
  tree.append(cm).unwrap();
  let witness = IncrementalWitness::from_tree(&tree);