title: Filter or search NSCollectionView on macOS 10.11+
body: <p>I'm looking for a way to filter the items displayed in an <code>NSCollectionView</code>. My <code>NSCollectionView</code> is managed using the 10.11 and up mechanism (i.e. with <code>NSCollectionViewDataSource</code> and <code>NSCollectionViewDelegate</code>). I can't seem to find any documentation on how this is done.</p>
  
  <p>Is it possible to implement a filter for the visible items, and if so, is there documentation available to show me how it is done?</p>