@Nullable
  private static String getRangeDescription(@NotNull Project project,
                                            int startLine,
                                            int endLine,
                                            int index,
                                            @NotNull DescriptionComputer computer) {
    if (startLine == endLine) return null;

    FoldedRangeDescription endDescription = computer.computeDescription(project, endLine, index);
    if (endDescription == null) return null;

    FoldedRangeDescription startDescription = computer.computeDescription(project, startLine, index);
    if (Comparing.equal(startDescription, endDescription) &&
        !(endDescription.anchorLine != -1 && startLine <= endDescription.anchorLine)) {
      return null;
    }
    return endDescription.description;
  }
@Nullable
  private static String getRangeDescription(@NotNull Project project,
                                            int startLine,
                                            int endLine,
                                            int index,
                                            @NotNull DescriptionComputer computer)