How to use the roosterjs-editor-core.Keys.U function in roosterjs-editor-core

/**
 * DefaultShortcut edit feature, provides shortcuts for the following features:
 * Ctrl/Meta+B: toggle bold style
 * Ctrl/Meta+I: toggle italic style
 * Ctrl/Meta+U: toggle underline style
 * Ctrl/Meta+Z: undo
 * Ctrl+Y/Meta+Shift+Z: redo
 * Ctrl/Meta+PERIOD: toggle bullet list
 * Ctrl/Meta+/: toggle numbering list
 * Ctrl/Meta+Shift+>: increase font size
 * Ctrl/Meta+Shift+<: decrease font size
 */
export const DefaultShortcut: ContentEditFeature = {
    allowFunctionKeys: true,
    keys: [Keys.B, Keys.I, Keys.U, Keys.Y, Keys.Z, Keys.COMMA, Keys.PERIOD, Keys.FORWARDSLASH],
    shouldHandleEvent: cacheGetCommand,
    handleEvent: (event, editor) => {
        let command = cacheGetCommand(event);
        if (command) {
            command.action(editor);
            event.rawEvent.preventDefault();
            event.rawEvent.stopPropagation();
        }
    },
};

function cacheGetCommand(event: PluginKeyboardEvent) {
    return cacheGetEventData(event, 'DEFAULT_SHORT_COMMAND', () => {
        let e = event.rawEvent;
        let key =
            // Need to check ALT key to be false since in some language (e.g. Polski) uses AltGr to input some special charactors

macKey: number;
    action: (editor: Editor) => any;
}

function createCommand(winKey: number, macKey: number, action: (editor: Editor) => any) {
    return {
        winKey,
        macKey,
        action,
    };
}

const commands: ShortcutCommand[] = [
    createCommand(Keys.Ctrl | Keys.B, Keys.Meta | Keys.B, toggleBold),
    createCommand(Keys.Ctrl | Keys.I, Keys.Meta | Keys.I, toggleItalic),
    createCommand(Keys.Ctrl | Keys.U, Keys.Meta | Keys.U, toggleUnderline),
    createCommand(Keys.Ctrl | Keys.Z, Keys.Meta | Keys.Z, editor => editor.undo()),
    createCommand(Keys.Ctrl | Keys.Y, Keys.Meta | Keys.Shift | Keys.Z, editor => editor.redo()),
    createCommand(Keys.Ctrl | Keys.PERIOD, Keys.Meta | Keys.PERIOD, toggleBullet),
    createCommand(Keys.Ctrl | Keys.FORWARDSLASH, Keys.Meta | Keys.FORWARDSLASH, toggleNumbering),
    createCommand(
        Keys.Ctrl | Keys.Shift | Keys.PERIOD,
        Keys.Meta | Keys.Shift | Keys.PERIOD,
        editor => changeFontSize(editor, FontSizeChange.Increase)
    ),
    createCommand(
        Keys.Ctrl | Keys.Shift | Keys.COMMA,
        Keys.Meta | Keys.Shift | Keys.COMMA,
        editor => changeFontSize(editor, FontSizeChange.Decrease)
    ),
];