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

function _prepareListOptions( options, command ) {
	const itemDefinitions = new Collection();

	// Create dropdown items.
	for ( const option of options ) {
		const def = {
			type: 'button',
			model: new Model( {
				commandName: FONT_FAMILY,
				commandParam: option.model,
				label: option.title,
				withText: true
			} )
		};

		def.model.bind( 'isOn' ).to( command, 'value', value => value === option.model );

		// Try to set a dropdown list item style.

_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 ) => {

constructor( doc ) {
		super();

		// List of selection markers.
		// Marker is a selection marker when selection range is inside the marker range.
		//
		// @type {module:utils/collection~Collection}
		this.markers = new Collection( { idProperty: 'name' } );

		// Document which owns this selection.
		//
		// @protected
		// @member {module:engine/model/model~Model}
		this._model = doc.model;

		// Document which owns this selection.
		//
		// @protected
		// @member {module:engine/model/document~Document}
		this._document = doc;

		// Keeps mapping of attribute name to priority with which the attribute got modified (added/changed/removed)
		// last time. Possible values of priority are: `'low'` and `'normal'`.
		//

function _prepareListOptions( options, command ) {
	const itemDefinitions = new Collection();

	for ( const option of options ) {
		const def = {
			type: 'button',
			model: new Model( {
				commandName: FONT_SIZE,
				commandParam: option.model,
				label: option.title,
				class: 'ck-fontsize-option',
				withText: true
			} )
		};

		if ( option.view && option.view.styles ) {
			def.model.set( 'labelStyle', `font-size:${ option.view.styles[ 'font-size' ] }` );
		}

* @member {module:engine/view/documentselection~DocumentSelection} module:engine/view/document~Document#selection
		 */
		this.selection = new DocumentSelection();

		/**
		 * Roots of the view tree. Collection of the {@link module:engine/view/element~Element view elements}.
		 *
		 * View roots are created as a result of binding between {@link module:engine/view/document~Document#roots} and
		 * {@link module:engine/model/document~Document#roots} and this is handled by
		 * {@link module:engine/controller/editingcontroller~EditingController}, so to create view root we need to create
		 * model root using {@link module:engine/model/document~Document#createRoot}.
		 *
		 * @readonly
		 * @member {Collection} module:engine/view/document~Document#roots
		 */
		this.roots = new Collection( { idProperty: 'rootName' } );

		/**
		 * Defines whether document is in read-only mode.
		 *
		 * When document is read-ony then all roots are read-only as well and caret placed inside this root is hidden.
		 *
		 * @observable
		 * @member {Boolean} #isReadOnly
		 */
		this.set( 'isReadOnly', false );

		/**
		 * True if document is focused.
		 *
		 * This property is updated by the {@link module:engine/view/observer/focusobserver~FocusObserver}.
		 * If the {@link module:engine/view/observer/focusobserver~FocusObserver} is disabled this property will not change.

/**
		 * Defines whether there is any registered pending action.
		 *
		 * @readonly
		 * @observable
		 * @member {Boolean} #hasAny
		 */
		this.set( 'hasAny', false );

		/**
		 * A list of pending actions.
		 *
		 * @private
		 * @type {module:utils/collection~Collection}
		 */
		this._actions = new Collection( { idProperty: '_id' } );
		this._actions.delegate( 'add', 'remove' ).to( this );
	}

* @member {module:engine/view/documentselection~DocumentSelection} module:engine/view/document~Document#selection
		 */
		this.selection = new DocumentSelection();

		/**
		 * Roots of the view tree. Collection of the {@link module:engine/view/element~Element view elements}.
		 *
		 * View roots are created as a result of binding between {@link module:engine/view/document~Document#roots} and
		 * {@link module:engine/model/document~Document#roots} and this is handled by
		 * {@link module:engine/controller/editingcontroller~EditingController}, so to create view root we need to create
		 * model root using {@link module:engine/model/document~Document#createRoot}.
		 *
		 * @readonly
		 * @member {module:utils/collection~Collection} module:engine/view/document~Document#roots
		 */
		this.roots = new Collection( { idProperty: 'rootName' } );

		/**
		 * Defines whether document is in read-only mode.
		 *
		 * When document is read-ony then all roots are read-only as well and caret placed inside this root is hidden.
		 *
		 * @observable
		 * @member {Boolean} #isReadOnly
		 */
		this.set( 'isReadOnly', false );

		/**
		 * True if document is focused.
		 *
		 * This property is updated by the {@link module:engine/view/observer/focusobserver~FocusObserver}.
		 * If the {@link module:engine/view/observer/focusobserver~FocusObserver} is disabled this property will not change.

/**
		 * The selection in this document.
		 *
		 * @readonly
		 * @type {module:engine/model/documentselection~DocumentSelection}
		 */
		this.selection = new DocumentSelection( this );

		/**
		 * A list of roots that are owned and managed by this document. Use {@link #createRoot} and
		 * {@link #getRoot} to manipulate it.
		 *
		 * @readonly
		 * @type {module:utils/collection~Collection}
		 */
		this.roots = new Collection( { idProperty: 'rootName' } );

		/**
		 * The model differ object. Its role is to buffer changes done on the model document and then calculate a diff of those changes.
		 *
		 * @readonly
		 * @type {module:engine/model/differ~Differ}
		 */
		this.differ = new Differ( model.markers );

		/**
		 * Post-fixer callbacks registered to the model document.
		 *
		 * @private
		 * @type {Set.}
		 */
		this._postFixers = new Set();