private static void convertInterfaceToClass(PsiClass anInterface, Collection<PsiClass> inheritors, @NotNull ModPsiUpdater updater) {
    final List<PsiClass> writableInheritors = ContainerUtil.map(inheritors, updater::getWritable);
    moveSubClassImplementsToExtends(anInterface, writableInheritors);
    changeInterfaceToClass(anInterface);
    moveExtendsToImplements(anInterface);
  }
private static void convertInterfaceToClass(PsiClass anInterface, Collection<PsiClass> inheritors, @NotNull ModPsiUpdater updater)