title: Is there a way to "Reverse" an NSPredicate
body: <p>Let's say that I have this predicate:</p>
  
  <pre><code>NSPredicate *filter = [NSPredicate predicateWithFormat:@"%K == NO", @"someAttribute"];
  </code></pre>
  
  <p>And I wish to reverse that predicate to :</p>
  
  <pre><code>NSPredicate *filter = [NSPredicate predicateWithFormat:@"%K == YES", @"someAttribute"];
  </code></pre>
  
  <p>Is there a way to do this without creating a new predicate.</p>