public static CommonProblemDescriptor @NotNull [] flattenDescriptors(@NotNull List<CommonProblemDescriptor[]> descriptors) {
    return descriptors.stream().flatMap(ds -> Arrays.stream(ds)).toArray(CommonProblemDescriptor.ARRAY_FACTORY::create);
  }
public static CommonProblemDescriptor @NotNull [] flattenDescriptors(@NotNull List<CommonProblemDescriptor[]> descriptors)