Calculate total working hours for employee in odoo

Question

class AttendanceEmp(models.Model):
    _name = 'shift.log'
    _description = 'Attendance'

    sh_id = fields.Many2one(comodel_name='hr.employee',string='emp id')
    checkin_or_checkout = fields.Datetime(string="start or end time", required=True)
    check_in = fields.Selection([('1','True'),('2','False')])

    def log_details_calculate(self):
        pass

this is my model and in this model check-in that return true and checkout that return false and i have added some employee check-in and checkout manually now i want to create logic that calculate any particular employee working hours. how can i do that to calculate total working hours for employee