@Override
  public final @NotNull List<FileASTNode> getKnownTreeRoots() {
    List<FileASTNode> files = new ArrayList<>(myRoots.size());
    for (PsiFileImpl file : myRoots.values()) {
      FileASTNode treeElement = file.getNodeIfLoaded();
      if (treeElement != null) {
        files.add(treeElement);
      }
    }

    return files;
  }
@Override
  public final @NotNull List<FileASTNode> getKnownTreeRoots()