title: cast from [String:AnyObject] to unrelated type NSMutableDictionary always fails Warning
body: <p>Code is working, but how do I silent this warning that keeps on appearing every time?</p>
  
  <pre><code>let parentView = self.parentViewController as! SBProfileViewController
  parentView.savedDetailsModel = SBSavedUserModel(data:responseObject["data"].dictionaryObject! as! NSMutableDictionary)
  </code></pre>
  
  <blockquote>
    <p>cast from '[String:AnyObject]' to unrelated type 'NSMutableDictionary' always fails Warning </p>
  </blockquote>
  
  <p>SavedUserModel stores saved information:--</p>
  
  <pre><code>class SBSavedUserModel : NSObject { 
  var userId : String!
  var firstName : String!
  var lastName : String!
  var imageBase64 : String!
  
  required init ( data : NSMutableDictionary) {
      self.userId =  data.objectForKey("userId") as! String
      self.firstName = data.objectForKey("fName") as! String
      self.lastName = data.objectForKey("lName") as! String
      self.imageBase64 = data.objectForKey("image") as! String
  }
  </code></pre>