How to get firestore document ID into a RecyclerView adapter?

I want to call firestore document ID into RecyclerView adapter. but not getting it how to do it. can someone help in relate to it. actually I want to add to fab functionality in my app using paper DB. so I want that it will take place using document ID because it's unique for every document. but not getting how to get document ID into adapter class so that I can use it.

Firestore Structure Image.

My Adapter Class:

public class CitiesAdapter extends RecyclerView.Adapter<CitiesAdapter.ViewHolder> {

    public List<Cities> citiesList;

    public CitiesAdapter(Context context, List<Cities> citiesList) {
        this.citiesList = citiesList;
    }

    @Override
    public int getItemCount() {
        return citiesList.size();
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View citiesView = LayoutInflater.from(parent.getContext()).inflate(R.layout.cardview_cities_you_must_visit, parent, false);
        return new ViewHolder(citiesView);
    }

    @Override
    public void onBindViewHolder(final CitiesAdapter.ViewHolder holder, final int position) {

            holder.vCityName.setText(citiesList.get(position).getmCityName() + ",");
       
    public class ViewHolder extends RecyclerView.ViewHolder {

        public TextView vCityName;
        
        View CityView;


        public ViewHolder(View itemView) {
            super(itemView);
            CityView = itemView;

            vCityName = CityView.findViewById(R.id.lCityName);
            
        }
    }

}

Home Fragment:

mFirestore.collection("Cities").addSnapshotListener(new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@javax.annotation.Nullable QuerySnapshot documentSnapshots, @javax.annotation.Nullable FirebaseFirestoreException e) {
                if (e != null) {
                }

                assert documentSnapshots != null;


                for (DocumentChange doc : documentSnapshots.getDocumentChanges()) {

                    if (doc.getType() == DocumentChange.Type.ADDED) {
                        String doc_id = doc.getDocument().getId();
                        Cities city = doc.getDocument().toObject(Cities.class).withDocId(doc_id);
                        cities.add(doc.getNewIndex(), city);
                        citiesAdapter.notifyDataSetChanged();

                    } else if (doc.getType() == DocumentChange.Type.MODIFIED) {
                        String docID = doc.getDocument().getId();
                        Cities changedModel = doc.getDocument().toObject(Cities.class).withDocId(docID);
                        if (doc.getOldIndex() == doc.getNewIndex()) {
                            // Item changed but remained in same position
                            cities.set(doc.getOldIndex(), changedModel);
                            citiesAdapter.notifyItemChanged(doc.getOldIndex());
                        } else {
                            // Item changed and changed position
                            cities.remove(doc.getOldIndex());
                            cities.add(doc.getNewIndex(), changedModel);
                            citiesAdapter.notifyItemMoved(doc.getOldIndex(), doc.getNewIndex());
                        }
                    } else if (doc.getType() == DocumentChange.Type.REMOVED) {
                        // remove
                        cities.remove(doc.getOldIndex());
                        citiesAdapter.notifyItemRemoved(doc.getOldIndex());
                    }
                }
            }
        });