code: protected function getFactory($type)
      {
          if (isset($this->selectorSourceFactories[$type])) {
              return $this->selectorSourceFactories[$type];
          } else {
              throw new \Exception("Factory \"$type\" not foud");
          }
      }
docs: get factory by its type
  @param $type
  @return Selector\SourceFactory\SelectorSourceFactoryInterface
  @throws \Exception