public void onAccordionClicked(int position) {
        List<ContactListModel> currentItems = _itemsLiveData.getValue();
        if (currentItems == null || currentItems.isEmpty() || position < 0 || position > currentItems.size()) return;
        ContactListModel selectedItem = currentItems.get(position);
        if (selectedItem instanceof RegionListItem) {
            if (((RegionListItem) selectedItem).isOpened()) {
                _itemsLiveData.postValue(removeChild(currentItems, ((RegionListItem) selectedItem), position));
                _itemsRangeInsertLiveData.postValue(new Pair<>(position + 1, ((RegionListItem) selectedItem).getContactListModels().size()));
            } else {
                _itemsLiveData.postValue(addChild(currentItems, ((RegionListItem) selectedItem), position));
                _itemsRemovedInsertLiveData.postValue(new Pair<>(position + 1, ((RegionListItem) selectedItem).getContactListModels().size()));
            }
            _itemForUpdateLiveData.postValue(position);
        }
    }

    private List<ContactListModel> removeChild(List<ContactListModel> items, RegionListItem item, int position) {
        for (int i = 1; i <= item.getContactListModels().size(); i++) {
            items.remove(position + 1);
        }
        items.set(position, new RegionListItem(item, false));
        return items;
    }

    private List<ContactListModel> addChild(List<ContactListModel> items, RegionListItem item, int position) {
        for (int i = 1; i <= item.getContactListModels().size(); i++) {
            items.add(position + i, item.getContactListModels().get(i - 1));
        }
        items.set(position, new RegionListItem(item, true));
        return items;
    }


// Fragment
  contactsController.itemsLiveData.observe(getViewLifecycleOwner(), contactListModels -> {
           adapter.submitList(contactListModels);
        });

        contactsController.itemForUpdateLiveData.observe(getViewLifecycleOwner(), position -> {
            adapter.notifyItemChanged(position);
        });

        contactsController.itemsRangeInsertLiveData.observe(getViewLifecycleOwner(), pair -> {
            adapter.notifyItemRangeInserted(pair.first, pair.second);
        });

        contactsController.itemsRemovedInsertLiveData.observe(getViewLifecycleOwner(), pair -> {
            adapter.notifyItemRangeRemoved(pair.first, pair.second);
        });