@NotNull public List<Pair<C,Collection<VirtualFile>>> createConfigurations(@NotNull Collection<VirtualFile> files,@NotNull Collection<C> existentFacetConfigurations){
  final C configuration=createConfiguration(files);
  if (configuration != null) {
    return Collections.singletonList(Pair.create(configuration,files));
  }
  return Collections.emptyList();
}

@ NotNull public List < Pair < C , Collection < VirtualFile > > > createConfigurations ( @ NotNull Collection < VirtualFile > files , @ NotNull Collection < C > existentFacetConfigurations ) { final C configuration = createConfiguration ( files ) ; if ( configuration != null ) { return Collections . singletonList ( Pair . create ( configuration , files ) ) ; } return Collections . emptyList ( ) ; }
override this method if several facets of this type are allowed in a single module
