many2many restrict selection based on a object property if similar object previously selected.

so i have a ranks records and those ranks are getting picked in  contact info

contact module: 

from odoo import models, fields, api, _
from odoo.exceptions import UserError


class res_partner_rank(models.Model):
    _inherit = 'res.partner'
    _description = 'ranking system inherit field'

    rank = fields.Many2many('ranks.system', string='Rank')

def check_selection(self):
    for rec in self:
        cats = []
        if len(rec.rank) > 0:
            for i, rank in enumerate(rec.rank):
                if len(rank[i].category_id) > 0:

this method should check if user has any rank that got the same product category.

rank module :

from odoo import models, fields, api, _
from odoo.exceptions import UserError


class ranks_system(models.Model):
    _name = 'ranks.system'
    name = fields.Char()
    description = fields.Text()
    priority = fields.Selection([('0', 'Public'), ('1', 'Bronze'), ('2', 'Silver'), ('3', "Gold"), ('4', "Platinum")])
    category_id = fields.Many2many('product.category', string='Category Satisfies The Discount')
    discount = fields.Float()
    rank_start_from = fields.Float(default=0, string='Class Ratio Starts From',
                                   help='Class ratio start from how much the Customer will pay')
    rank_ends_to = fields.Float(default=1, string='Class Ratio Ends To',
                                help='Class ratio end to how much the Customer will pay')

    @api.onchange('rank_inv_to')
    def rank_check(self):
        for rec in self:
            if rec.rank_ends_to < rec.rank_start_from:
                raise UserError(_("Class " + str(rec.name) + " invoicing End " + str(
                    rec.rank_ends_to) + " Can't be less than Invoicing Start " + str(rec.rank_start_from)))