private void addUsages(CompilerRef usage, Set<VirtualFile> sink) throws StorageException {
      myIndex.get(JavaCompilerIndices.BACK_USAGES).getData(usage).forEach(
        (id, value) -> {
          final VirtualFile file = findFile(id);
          if (file != null) {
            sink.add(file);
          }
          return true;
        });
    }
private void addUsages(CompilerRef usage, Set<VirtualFile> sink)