Optionaloptions: Partial<TreeIterator.Options>tslint:disable-next-line:typedef
ProtectedchildrenProtecteddoProtectedisProtectedisProtectediteratorProtectedlastNOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
Unlike other tree iterators, this does not visit all the nodes, it stops once it reaches the root node while traversing up the tree hierarchy in an inverse pre-order fashion. This is the counterpart of the
TopDownTreeIterator.