i have created a Master-Detail page and it works fine. Countries -> States

now i want to add further Cities which are depends on States , how I can add in model and view (xml) to achieve (the best approach). i am copying my model and xml files contents, please check and guide me to add Cities here as details (child) of States.

Model:

from odoo import models, fields, api


class HospitalCountries(models.Model):
    _name = 'hospital.countries'
    _description = "Countries"

    name = fields.Text(string="Country Name", required=True)
    slug = fields.Char(string="Slug")

    country_ids = fields.One2many('hospital.states', 'country_id')


class HospitalStates(models.Model):
    _name = 'hospital.states'
    _description = "States"

    name = fields.Text(string="State Name", required=True)
    country_id = fields.Many2one('hospital.countries', "Country", required=True)

    state_ids = fields.One2many('hospital.cities', 'state_id')


class HospitalCities(models.Model):
    _name = 'hospital.cities'
    _description = "Cities"

    name = fields.Text(string="City Name", required=True)
    country_id = fields.Many2one('hospital.countries', "Country", required=True)
    state_id = fields.Many2one('hospital.states', "State", required=True, domain="[('country_id', '=', country_id)]")

View (xml):



    
    ir\.ui\.view"\ id="locations_form_view">
\ \ \ \ \ \ \ \ locations\.form
\ \ \ \ \ \ \ \ hospital\.countries
\ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ \ \ \ \ 
\ \ \ \ \ \ \ \ 
\ \ \ \ 


\ \ \ \ ir.ui.view" id="locations_tree_view">
        locations.tree
        hospital.countries
        
            
                
                
            
        
    

    
        Locations
        ir.actions.act_window
        hospital.countries
        tree,form
    

                id="menu_locations"
            name="Locations"
            parent="menu_hospital_operations"
            action="action_hospital_locations"
            sequence="-11"/>


regards