How to use the @ckeditor/ckeditor5-ui/src/dropdown/utils.addListToDropdown function in @ckeditor/ckeditor5-ui

editor.ui.componentFactory.add( FONT_SIZE, locale => {
			const dropdownView = createDropdown( locale );
			addListToDropdown( dropdownView, _prepareListOptions( options, command ) );

			// Create dropdown model.
			dropdownView.buttonView.set( {
				label: t( 'Font Size' ),
				icon: fontSizeIcon,
				tooltip: true
			} );

			dropdownView.extendTemplate( {
				attributes: {
					class: [
						'ck-font-size-dropdown'
					]
				}
			} );

_prepareDropdown( label, icon, options, locale ) {
		const editor = this.editor;

		const dropdownView = createDropdown( locale );
		const commands = [];

		// Prepare dropdown list items for list dropdown.
		const itemDefinitions = new Collection();

		for ( const option of options ) {
			addListOption( option, editor, commands, itemDefinitions );
		}

		addListToDropdown( dropdownView, itemDefinitions );

		// Decorate dropdown's button.
		dropdownView.buttonView.set( {
			label,
			icon,
			tooltip: true
		} );

		// Make dropdown button disabled when all options are disabled.
		dropdownView.bind( 'isEnabled' ).toMany( commands, 'isEnabled', ( ...areEnabled ) => {
			return areEnabled.some( isEnabled => isEnabled );
		} );

		this.listenTo( dropdownView, 'execute', evt => {
			editor.execute( evt.source.commandName );
			editor.editing.view.focus();

editor.ui.componentFactory.add( FONT_FAMILY, locale => {
			const dropdownView = createDropdown( locale );
			addListToDropdown( dropdownView, _prepareListOptions( options, command ) );

			dropdownView.buttonView.set( {
				label: t( 'Font Family' ),
				icon: fontFamilyIcon,
				tooltip: true
			} );

			dropdownView.extendTemplate( {
				attributes: {
					class: 'ck-font-family-dropdown'
				}
			} );

			dropdownView.bind( 'isEnabled' ).to( command );

			// Execute command when an item from the dropdown is selected.