How to use the @ckeditor/ckeditor5-ui/src/viewcollection function in @ckeditor/ckeditor5-ui

/**
     * A button used to cancel the form.
     *
     * @member {module:ui/button/buttonview~ButtonView} #cancelButtonView
     */
    this.cancelButtonView = this._createButton( t( 'Cancel' ), 'cancel' );

    /**
     * A collection of views which can be focused in the form.
     *
     * @readonly
     * @protected
     * @member {module:ui/viewcollection~ViewCollection}
     */
    this._focusables = new ViewCollection();

    /**
     * Helps cycling over {@link #_focusables} in the form.
     *
     * @readonly
     * @protected
     * @member {module:ui/focuscycler~FocusCycler}
     */
    this._focusCycler = new FocusCycler( {
      focusables: this._focusables,
      focusTracker: this.focusTracker,
      keystrokeHandler: this.keystrokes,
      actions: {
        // Navigate form fields backwards using the Shift + Tab keystroke.
        focusPrevious: 'shift + tab',

* The Smile button view.
		 *
		 * @member {module:ui/button/buttonview~ButtonView}
		 */
		editor.config.get( 'emoji' ).forEach( emoji => {
			this.emojiButtonViews.add( this._createButton( emoji.text, 'emoji:' + emoji.name ) );
		} );

		/**
		 * A collection of views which can be focused in the form.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/viewcollection~ViewCollection}
		 */
		this._focusables = new ViewCollection();

		/**
		 * Helps cycling over {@link #_focusables} in the form.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/focuscycler~FocusCycler}
		 */
		this._focusCycler = new FocusCycler( {
			focusables: this._focusables,
			focusTracker: this.focusTracker,
			keystrokeHandler: this.keystrokes,
			actions: {
				// Navigate form fields backwards using the Shift + Tab keystroke.
				focusPrevious: 'shift + tab',

/**
		 * The Cancel button view.
		 *
		 * @member {module:ui/button/buttonview~ButtonView}
		 */
		this.cancelButtonView = this._createButton( t( 'Cancel' ), cancelIcon, 'ck-button-cancel', 'cancel' );

		/**
		 * A collection of views that can be focused in the form.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/viewcollection~ViewCollection}
		 */
		this._focusables = new ViewCollection();

		/**
		 * Helps cycling over {@link #_focusables} in the form.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/focuscycler~FocusCycler}
		 */
		this._focusCycler = new FocusCycler( {
			focusables: this._focusables,
			focusTracker: this.focusTracker,
			keystrokeHandler: this.keystrokes,
			actions: {
				// Navigate form fields backwards using the Shift + Tab keystroke.
				focusPrevious: 'shift + tab',

/**
		 * A button used to cancel the form.
		 *
		 * @member {module:ui/button/buttonview~ButtonView} #cancelButtonView
		 */
		this.cancelButtonView = this._createButton( t( 'Cancel' ), cancelIcon, 'ck-button-cancel', 'cancel' );

		/**
		 * A collection of views which can be focused in the form.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/viewcollection~ViewCollection}
		 */
		this._focusables = new ViewCollection();

		/**
		 * Helps cycling over {@link #_focusables} in the form.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/focuscycler~FocusCycler}
		 */
		this._focusCycler = new FocusCycler( {
			focusables: this._focusables,
			focusTracker: this.focusTracker,
			keystrokeHandler: this.keystrokes,
			actions: {
				// Navigate form fields backwards using the Shift + Tab keystroke.
				focusPrevious: 'shift + tab',

/**
     * A button used to cancel the form.
     *
     * @member {module:ui/button/buttonview~ButtonView} #cancelButtonView
     */
    this.cancelButtonView = this._createButton( t( 'Cancel' ), 'cancel' );

    /**
     * A collection of views which can be focused in the form.
     *
     * @readonly
     * @protected
     * @member {module:ui/viewcollection~ViewCollection}
     */
    this._focusables = new ViewCollection();

    /**
     * Helps cycling over {@link #_focusables} in the form.
     *
     * @readonly
     * @protected
     * @member {module:ui/focuscycler~FocusCycler}
     */
    this._focusCycler = new FocusCycler( {
      focusables: this._focusables,
      focusTracker: this.focusTracker,
      keystrokeHandler: this.keystrokes,
      actions: {
        // Navigate form fields backwards using the Shift + Tab keystroke.
        focusPrevious: 'shift + tab',

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: {
				// Navigate form fields backwards using the Shift + Tab keystroke.
				focusPrevious: 'shift + tab',
				// Navigate form fields forwards using the Tab key.
				focusNext: 'tab'
			}
		} );

		const bind = this.bindTemplate;

/**
		 * 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 => {
			this.emojiButtonViews.add( this._createButton( emoji.text, 'emoji:' + emoji.name ) );
		} );

		/**
		 * A collection of views which can be focused in the form.
		 *
		 * @readonly
		 * @protected
		 * @member {module:ui/viewcollection~ViewCollection}