code: public static <T, U> SameType<T> of(TreeNode<T> expected, TreeDef<U> treeDef, U actual, Function<? super U, ? extends T> mapper) {
  		return of(TreeNode.treeDef(), expected, treeDef, actual).mapToSame(TreeNode::getContent, mapper);
  	}
docs: Creates a {@link SameType} for comparing a {@link TreeNode} against a generic tree which been mapped.