I want to save an odoo form with atleast one field should be different and no duplicate saving of form

I have created a form where i want to store all the information by filling it out, but the condition is there should not be any duplicate entry with same entries in all the fields, atleast one different entry will work..

Here is my code-

class HRLeaveRules(models.Model):
    _name = 'hr_leave_rules.leave_rules'
    half_day_allowed = fields.Selection([
        ('yes',"Yes"),
        ('no',"No")],
        string="Half Day Allowed", required=True)
    gender_specific = fields.Selection([
        ('all' ,"All"),
        ('male',"Male"),
        ('female',"Female")],
        string="Gender Specific", required=True)    
    leaves_allowed_on_prorata_basis = fields.Selection([
        ('yes',"Yes"),
        ('no',"No")],
        string="Leaves allowed on pro rata basis", required=True)
    leave_encashment = fields.Boolean(string="Leave Encashment", 
        required=True)
    leave_encashment_for_maximum = fields.Integer(
        string = "Leave Encashment for maximum", required=True)     
    can_emp_club_leave = fields.Selection([
        ('yes',"Yes"),
        ('no',"No")],
        string="Can Employees Club this leave with any other leave", 
        required=True)  
    past_dated_leave_allowed = fields.Selection([
        ('yes',"Yes"),
        ('no',"No")],
        string="Past dated leave application allowed", required=True)   
    override_paid_leave_to_unpaid = fields.Selection([
        ('yes',"Yes"),
        ('no',"No")],
        string="Can managers override paid leaves to unpaid", required=True)    
    carry_frwrdng_leaves = fields.Boolean(string="Carry forwarding of leaves", 
        required=True)  
    maximum_accumulation_in_year = fields.Integer(string = "Maximum Accumulation in year", 
        required=True)  
    leave_encash_rest_leaves = fields.Selection([
        ('yes',"Yes"),
        ('no',"No")],
        string="Leave Encashment for Rest Leaves", required=True)
    employee_id = fields.Many2one('hr.employee', string="Employee")
    holiday_status_id = fields.Many2one("hr.holidays.status", 
        string="Leave Type", required=True) 
    department_id = fields.Many2one('hr.department', 
        related='employee_id.department_id', string='Department') 
    count_intervening_leaves = fields.Boolean(
        string="Count intervening holidays/weekly offs as leaves", 
        required=True)
    count_intervening_leaves_back_date = fields.Boolean(
        string="Count intervening holidays/weekly offs as leaves if applying for back date", 
        required=True)
    leaves_probation_period = fields.Boolean(string="Leaves allowed in probation period", 
        required=True)
    max_con_leaves_month = fields.Boolean(string="Maximum consecutive leaves per month", 
        required=True)
    leave_encashment_cycle = fields.Selection([
        ('annually',"Annually"),
        ('super_annuation',"Super Annuation / Relieving")],
        string="Leave Encashment Cycle", required=True)
    description = fields.Text(string="Description")

    @api.model
    def create(self,value):
        current = self.env['hr_leave_rules.leave_rules'].search([])
        for rec in current:
            if value.has_key("holiday_status_id"):
                if rec.holiday_status_id.id == value["holiday_status_id"] and rec.holiday_status_id:
                    if value.has_key("gender_specific"):
                        if rec.gender_specific == value["gender_specific"] and rec.gender_specific:                 
                            if value.has_key("half_day_allowed"):
                                if rec.half_day_allowed == value["half_day_allowed"] and rec.half_day_allowed:                  
                                    if value.has_key("leaves_allowed_on_prorata_basis"):
                                        if rec.leaves_allowed_on_prorata_basis == value["leaves_allowed_on_prorata_basis"] and rec.leaves_allowed_on_prorata_basis:                 
                                            if value.has_key("leave_encashment_cycle"):
                                                if rec.leave_encashment_cycle == value["leave_encashment_cycle"] and rec.leave_encashment_cycle:
                                                    if value.has_key("leave_encash_rest_leaves"):
                                                        if rec.leave_encash_rest_leaves == value["leave_encash_rest_leaves"] and rec.leave_encash_rest_leaves:                                                  
                                                            if value.has_key("can_emp_club_leave"):
                                                                if rec.can_emp_club_leave == value["can_emp_club_leave"] and rec.can_emp_club_leave:
                                                                    if value.has_key("past_dated_leave_allowed"):
                                                                        if rec.past_dated_leave_allowed == value["past_dated_leave_allowed"] and rec.past_dated_leave_allowed:
                                                                            if value.has_key("override_paid_leave_to_unpaid"):
                                                                                if rec.override_paid_leave_to_unpaid == value["override_paid_leave_to_unpaid"] and rec.override_paid_leave_to_unpaid:
                                                                                    raise UserError(_('This type of leave already exist in the leave rules !'))

Condition for no duplicate entry is working properly but the unique form is not saving information

The error is -

AttributeError: 'NoneType' object has no attribute 'id'