private void OnEnable()
        {
            if (_treeViewState == null)
            {
                _treeViewState = new TreeViewState();
            }

            _treeView    = new BehaviorTreeNodeModelView(_treeViewState);
            _searchField = new SearchField();
            _searchField.downOrUpArrowKeyPressed += _treeView.SetFocusAndEnsureSelectedItem;
        }
        void InitIfNeeded()
        {
            if (!_initialized)
            {
                if (_treeViewState == null)
                {
                    _treeViewState = new TreeViewState();
                }

                _treeView = new BehaviorTreeNodeModelView(_treeViewState);

                _searchField = new SearchField();
                _searchField.downOrUpArrowKeyPressed += _treeView.SetFocusAndEnsureSelectedItem;

                _initialized = true;
            }
        }