How to use the @ckeditor/ckeditor5-utils/src/focustracker function in @ckeditor/ckeditor5-utils

* An instance of the {@link module:ui/componentfactory~ComponentFactory}, a registry used by plugins
		 * to register factories of specific UI components.
		 *
		 * @readonly
		 * @member {module:ui/componentfactory~ComponentFactory} #componentFactory
		 */
		this.componentFactory = new ComponentFactory( editor );

		/**
		 * Stores the information about the editor UI focus and propagates it so various plugins and components
		 * are unified as a focus group.
		 *
		 * @readonly
		 * @member {module:utils/focustracker~FocusTracker} #focusTracker
		 */
		this.focusTracker = new FocusTracker();

		/**
		 * Fires throttled {@link module:core/editor/editorui~EditorUI#event:update} event.
		 *
		 * @protected
		 * @type {Function}
		 */
		this._throttledUpdate = throttle( () => this.fire( 'update' ), 5 );

		// Informs UI components that should be refreshed after layout change.
		this.listenTo( editor.editing.view.document, 'layoutChanged', () => this.update() );
	}

* An instance of the {@link module:ui/componentfactory~ComponentFactory}, a registry used by plugins
		 * to register factories of specific UI components.
		 *
		 * @readonly
		 * @member {module:ui/componentfactory~ComponentFactory} #componentFactory
		 */
		this.componentFactory = new ComponentFactory( editor );

		/**
		 * Stores the information about the editor UI focus and propagates it so various plugins and components
		 * are unified as a focus group.
		 *
		 * @readonly
		 * @member {module:utils/focustracker~FocusTracker} #focusTracker
		 */
		this.focusTracker = new FocusTracker();

		/**
		 * Stores all editable elements used by the editor instance.
		 *
		 * @private
		 * @member {Map.}
		 */
		this._editableElementsMap = new Map();

		// Informs UI components that should be refreshed after layout change.
		this.listenTo( editor.editing.view.document, 'layoutChanged', () => this.update() );
	}

this.items = this.createCollection();

		/**
		 * An array with objects representing colors to be displayed in the grid.
		 *
		 * @type {Arrray.}
		 */
		this.colorDefinitions = colors;

		/**
		 * Tracks information about the DOM focus in the list.
		 *
		 * @readonly
		 * @member {module:utils/focustracker~FocusTracker}
		 */
		this.focusTracker = new FocusTracker();

		/**
		 * An instance of the {@link module:utils/keystrokehandler~KeystrokeHandler}.
		 *
		 * @readonly
		 * @member {module:utils/keystrokehandler~KeystrokeHandler}
		 */
		this.keystrokes = new KeystrokeHandler();

		/**
		 * Keeps the value of the command associated with the table for the current selection.
		 *
		 * @type {String}
		 */
		this.set( 'selectedColor' );

constructor( locale ) {
    super( locale );

    const t = this.locale.t;

    /**
     * Tracks information about DOM focus in the form.
     *
     * @readonly
     * @member {module:utils/focustracker~FocusTracker}
     */
    this.focusTracker = new FocusTracker();

    /**
     * An instance of the {@link module:utils/keystrokehandler~KeystrokeHandler}.
     *
     * @readonly
     * @member {module:utils/keystrokehandler~KeystrokeHandler}
     */
    this.keystrokes = new KeystrokeHandler();

    /**
     * A textarea with a label.
     *
     * @member {module:ui/labeledinput/labeledinputview~LabeledInputView} #labeledTextarea
     */
    this.formIdInput = this._createFormIdInputView();

constructor( locale ) {
		super( locale );

		const t = this.locale.t;

		/**
		 * Tracks information about the DOM focus in the form.
		 *
		 * @readonly
		 * @member {module:utils/focustracker~FocusTracker}
		 */
		this.focusTracker = new FocusTracker();

		/**
		 * An instance of the {@link module:utils/keystrokehandler~KeystrokeHandler}.
		 *
		 * @readonly
		 * @member {module:utils/keystrokehandler~KeystrokeHandler}
		 */
		this.keystrokes = new KeystrokeHandler();

		/**
		 * A textarea with a label.
		 *
		 * @member {module:ui/labeledinput/labeledinputview~LabeledInputView} #labeledTextarea
		 */
		this.labeledInput = this._createLabeledInputView();

constructor( validators, locale ) {
		super( locale );

		const t = locale.t;

		/**
		 * Tracks information about DOM focus in the form.
		 *
		 * @readonly
		 * @member {module:utils/focustracker~FocusTracker}
		 */
		this.focusTracker = new FocusTracker();

		/**
		 * An instance of the {@link module:utils/keystrokehandler~KeystrokeHandler}.
		 *
		 * @readonly
		 * @member {module:utils/keystrokehandler~KeystrokeHandler}
		 */
		this.keystrokes = new KeystrokeHandler();

		/**
		 * The URL input view.
		 *
		 * @member {module:ui/labeledinput/labeledinputview~LabeledInputView}
		 */
		this.urlInputView = this._createUrlInput();

constructor( locale ) {
    super( locale );

    const t = this.locale.t;

    /**
     * Tracks information about DOM focus in the form.
     *
     * @readonly
     * @member {module:utils/focustracker~FocusTracker}
     */
    this.focusTracker = new FocusTracker();

    /**
     * An instance of the {@link module:utils/keystrokehandler~KeystrokeHandler}.
     *
     * @readonly
     * @member {module:utils/keystrokehandler~KeystrokeHandler}
     */
    this.keystrokes = new KeystrokeHandler();

    /**
     * A textarea with a label.
     *
     * @member {module:ui/labeledinput/labeledinputview~LabeledInputView} #labeledTextarea
     */
    this.labeledInput = this._createLabeledInputView();

constructor( editor ) {
		super( editor.locale );

		/**
		 * Tracks information about DOM focus in the form.
		 *
		 * @readonly
		 * @member {module:utils/focustracker~FocusTracker}
		 */
		this.focusTracker = new FocusTracker();

		/**
		 * An instance of the {@link module:utils/keystrokehandler~KeystrokeHandler}.
		 *
		 * @readonly
		 * @member {module:utils/keystrokehandler~KeystrokeHandler}
		 */
		this.keystrokes = new KeystrokeHandler();
		this.emojiButtonViews = new ViewCollection( editor.locale );

		/**
		 * The Smile button view.
		 *
		 * @member {module:ui/button/buttonview~ButtonView}
		 */
		editor.config.get( 'emoji' ).forEach( emoji => {

constructor( engine, locale ) {
		super( locale );

		const t = locale.t;
		this.math         = new Utils.MathObject();
		
		this.focusTracker = new FocusTracker();  //Tracks information about DOM focus in the form.
		this.keystrokes   = new KeystrokeHandler();

		//----ui elements
		this.radioGroup_latexMode = this._createModeInput(); 
		this.latexRender          = new LatexRenderView(engine, this.locale);
		this.bottomPanel    = new HorizontalPanel(this.locale.t, [this.radioGroup_latexMode]);
		
		//----A collection of views which can be focused in the form.
		this._focusables = new ViewCollection();

		//----Helps cycling over {@link #_focusables} in the form.
		this._focusCycler = new FocusCycler( {
			focusables: this._focusables,
			focusTracker: this.focusTracker,
			keystrokeHandler: this.keystrokes,
			actions: {

/**
		 * Collection of the child tile views.
		 *
		 * @readonly
		 * @member {module:ui/viewcollection~ViewCollection}
		 */
		this.items = this.createCollection();

		/**
		 * Tracks information about DOM focus in the grid.
		 *
		 * @readonly
		 * @member {module:utils/focustracker~FocusTracker}
		 */
		this.focusTracker = new FocusTracker();

		/**
		 * Instance of the {@link module:utils/keystrokehandler~KeystrokeHandler}.
		 *
		 * @readonly
		 * @member {module:utils/keystrokehandler~KeystrokeHandler}
		 */
		this.keystrokes = new KeystrokeHandler();

		/**
		 * Helps cycling over focusable {@link #items} in the grid.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/focuscycler~FocusCycler}
		 */