code: protected function getSource($selectorSourceName)
      {
          if (false === isset($this->sources[$selectorSourceName])) {
              $this->sources[$selectorSourceName] = $this->getFactory($selectorSourceName)->getSource();
          }
  
          return $this->sources[$selectorSourceName];
      }
docs: Get a source by it's name
  @param $selectorSourceName
  @return \Yucca\Component\Selector\Source\SelectorSourceInterface
  @throws \InvalidArgumentException