title: What is a Predicate Delegate and where should it be used?
body: <p>Can you explain to me:</p>
  
  <ul>
  <li>What is a Predicate Delegate?</li>
  <li>Where should we use predicates?</li>
  <li>Any best practices when using predicates?</li>
  </ul>
  
  <p>Descriptive source code will be appreciated.</p>