public synchronized void increment(@NotNull String groupName,
                                     @NotNull NotificationSource source,
                                     @NotNull NotificationCategory category,
                                     @NotNull ProjectSystemId projectSystemId) {
    Object2IntMap<NotificationCategory> counter = map.computeIfAbsent(projectSystemId, __ -> new HashMap<>())
      .computeIfAbsent(groupName, __ -> new HashMap<>())
      .computeIfAbsent(source, __ -> new Object2IntOpenHashMap<>());
    counter.mergeInt(category, 1, Math::addExact);
  }
public synchronized void increment(@NotNull String groupName,
                                     @NotNull NotificationSource source,
                                     @NotNull NotificationCategory category,
                                     @NotNull ProjectSystemId projectSystemId)