         return _removeNavigationTitleItemButton(at: _navigationTitleItems.index(before: _navigationTitleItems.endIndex))
     }
     
+    // MARK: NavigationTitle Action Item
+    
     public func addNavigationTitleActionItem(_ item: TabNavigationTitleActionItem) {
         addNavigationTitleItem(item)
     }

        }
        return _navigationTitleItems[_selectedTitleItemIndex]
    }
    
    public var navigationItems: [TabNavigationItem] {
        set(items) {
            for item in items {

            }
        }
    }
    
    // MARK: - Tab transitions.
    
    public func beginTransitionNavigationItems(_ items: [TabNavigationItem], on navigatiomItems: [TabNavigationItem] = [], `in` itemViews: TabNavigationItemViews? = nil) -> TabNavigationItemViews {
        if !navigatiomItems.isEmpty {
