lastDeepestVisibleChild() {
        let found;

        if (this.hasChildren() && !this.collapsed()) {
            found = findLast(this.children, node => node.visible());

            const res = found.lastDeepestVisibleChild();
            if (res) {
                found = res;
            }
        }

        return found;
    }
Find the last + deepest visible child of the previous sibling.

@return {TreeNode} Node object.