public function testReturningACollectionAsJasonWillSafelyRepresentDateTimes()
 {
     $collection = new GraphNode(['id' => '123', 'date' => new \DateTime('2014-07-15T03:44:53+0000')]);
     $collectionAsString = $collection->asJson();
     $this->assertEquals('{"id":"123","date":"2014-07-15T03:44:53+0000"}', $collectionAsString);
 }
 public function extractBiggestImageFromNode(GraphNode $node)
 {
     if ($node->offsetExists(0)) {
         return $node->offsetGet(0)['source'];
     } else {
         foreach ($node as $image) {
             return $image['source'];
         }
     }
     return null;
 }