private static @Nullable FrameDiffTool findToolSubstitutor(@NotNull DiffTool tool,
                                                             @NotNull DiffContext diffContext,
                                                             @NotNull DiffRequest diffRequest) {
    DiffTool substitutor = DiffUtil.findToolSubstitutor(tool, diffContext, diffRequest);
    return substitutor instanceof FrameDiffTool ? (FrameDiffTool)substitutor : null;
  }
private static @Nullable FrameDiffTool findToolSubstitutor(@NotNull DiffTool tool,
                                                             @NotNull DiffContext diffContext,
                                                             @NotNull DiffRequest diffRequest)