title: How to check if key exists in swiftyJSON when json contain array with no keys
body: <p>I know about swiftyJSON method exists() but it does not seem to work always as they say.
  How can I get proper result in this case below? I cannot change JSON structure because I am getting this through client's API.</p>
  
  <pre><code>var json: JSON =  ["response": ["value1","value2"]]
  if json["response"]["someKey"].exists(){
      print("response someKey exists")
  }
  </code></pre>
  
  <p>Output:</p>
  
  <pre>
  response someKey exists
  </pre>
  
  <p>That shouldn't be printed because someKey does not exist. But sometimes that key comes from client's API, and i need to find out if it exists or not properly.</p>