title: get key by name from NSDictionary
body: <p>I have a nested NSDictionary of NSDictionaries. 
  I get the dictionaries in an NSArray *array and I iterate through them with <code>for (NSDictionary *frame in array)</code></p>
  
  <p>What I want is the name of the frame. For example [frame getName], is there any function for this?</p>