         return Selector(_selector)
     }
     
+    internal var underlyingView: UIView { return _view }
     fileprivate var _view: _TabNavigationItemView = _TabNavigationItemView()
     
     public init(title: String?) {

            _navigationBackItem._view.isHidden = false
        }
        if animated {
            UIView.animate(withDuration: 0.5, delay: 0.0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0.8, options: [], animations: { [unowned self] in
                self.layoutIfNeeded()
                }, completion: { [unowned self] finished in
                if finished && !shows {
                    self._navigationBackItem._view.isHidden = true
                }
            })
        }

        _calculateWidthConstantOfContentAlignmentView()
    }
    
    public func setNavigationTitleItems(_ items: [TabNavigationTitleItem], animated: Bool = false, selectedIndex index: Array<TabNavigationTitleItem>.Index = 0, actionsConfig: (() -> (ignore: Bool, actions: [TabNavigationTitleActionItem]?))? = nil, animation: ((TabNavigationTitleItemAnimationViews) -> Void)? = nil) {
        _setNavigationTitleItems(items, animated: animated, selectedIndex: index, actionConfig: actionsConfig?() ?? (false, nil), animation: animation)
    }
    @discardableResult
