@NotNull
  UpdatableIndex<K, V, FileContent, ?> createIndexImplementation(@NotNull FileBasedIndexExtension<K, V> extension,
                                                                 @NotNull VfsAwareIndexStorageLayout<K, V> indexStorageLayout)
    throws StorageException, IOException;
@NotNull
  UpdatableIndex<K, V, FileContent, ?> createIndexImplementation(@NotNull FileBasedIndexExtension<K, V> extension,
                                                                 @NotNull VfsAwareIndexStorageLayout<K, V> indexStorageLayout)