I want to check before creating/editing whether the employee has had a "Sales table" before, the condition is that an employee only has 1 sales table in 1 year.

The problem I'm having is that employee B has never created a Sales table but I get an error message "The {self.year} Sales table has been prepared for {self.employee_id.name} employees"

Here is my code:

class SalesTable(models.Model):
    _name = "sales.table"
    _description = "Bảng doanh số"
    _order = "year"

    name = fields.Char(string="Name sales table")
    company_id = fields.Many2one(comodel_name="res.company", string="Applies to companies",
                                 default=lambda self: self.env.company)
    year = fields.Char(string="Year", default=lambda self: datetime.date.today().year, readonly=True)
    employee_id = fields.Many2one(comodel_name="hr.employee")
    groups_employee = fields.One2many(comodel_name="group.employee", inverse_name="sales_table_id")
    line_ids = fields.One2many(comodel_name="sales.table.line", inverse_name="sales_table_id")
    type = fields.Selection(selection=[('single', "Single"), ('group', 'Group')], default='single', string="Type")

    @api.constrains("line_ids")
    def _check_validate_max_one_line(self):
        for r in self:
            if len(r.line_ids) > 1:
                raise UserError("Doanh số chỉ được 1 dòng")
            if len(r.line_ids) == 0:
                raise UserError("Doanh số chưa được đặt")

    @api.constrains("employee_id")
    def _check_validate_employee(self):
        for r in self:
            sales_tables = self.search(
                [('employee_id', '=', r.employee_id.id), ('year', '=', r.year)])
            if sales_tables:
                raise UserError(f"The {r.year} Sales table has been prepared for {r.employee_id.name} employees")