/**
  * @inheritdoc
  */
 public function findById($sourceId)
 {
     if (null === ($source = $this->findCachedById($sourceId))) {
         $source = $this->sourceManager->findById($sourceId);
         $this->cache($source);
     }
     return $source;
 }
 /**
  * @param integer $sourceId
  *
  * @return SourceInterface
  */
 protected function findSource($sourceId)
 {
     return $this->sourceManager->findById($sourceId);
 }