/**
  * Get a ConceptSearchSourceCollection of sources for the specified search group
  * @param ConceptSearchGroup $csg
  * @param ConceptSearch $cs
  * @return ConceptSearchSourceCollection
  */
 private function getSearchGroupSources(ConceptSearch $cs, ConceptSearchGroup $csg)
 {
     if ($arr_source = $csg->getInlineSources()) {
         // TODO: Get ConceptSearchSource objects for the referenced inline sources
         return null;
     } else {
         return $cs->getSelectedSources();
     }
 }