@Override
  public <Key> int getMaxContainingFileCount(@NotNull StubIndexKey<Key, ?> indexKey,
                                             @NotNull Key dataKey,
                                             @NotNull Project project,
                                             @NotNull GlobalSearchScope scope) {
    IntSet result = getContainingIds(indexKey, dataKey, project, null, scope);
    return result == null ? 0 : result.size();
  }
@Override
  public <Key> int getMaxContainingFileCount(@NotNull StubIndexKey<Key, ?> indexKey,
                                             @NotNull Key dataKey,
                                             @NotNull Project project,
                                             @NotNull GlobalSearchScope scope)