         }
     }
 }
-
+// MARK: Conforming of ExpressibleByStringLiteral.
 extension TabNavigationController.NavigationTitle: ExpressibleByStringLiteral {
     /// Extended grapheme cluster literal type.
     public typealias ExtendedGraphemeClusterLiteralType = Character

    /// Creates the .NavigationTitle value with an unicode scalar literal type value by conforms to protocol
    /// ExpressibleByStringLiteral.
    ///
    /// - Parameter unicodeScalarLiteral: An value of unicode scalar literal type to generate the .NavigationTitle value.
    /// - Return: A new value of .NavigationTitle with the given parameter.
    public init(unicodeScalarLiteral value: TabNavigationController.NavigationTitle.UnicodeScalarLiteralType) {
        self.init(extendedGraphemeClusterLiteral: Character(value))
    }
}

extension TabNavigationController.NavigationTitle: ExpressibleByDictionaryLiteral {
    public typealias Key = String
    public typealias Value = Any
    
    public init(dictionaryLiteral elements: (String, Any)...) {
        var _title: String?
        var _range: CountableRange<Int>?

    /// The default height of the tab navigation bar.
    var tabNavigationBarHeight: CGFloat { return 64.0 }
}
// MARK: NavigationTitle.
public extension TabNavigationController {
    /// A type indicates the selected tab title item storage.
    public struct NavigationTitle {
