Hiii,

I am a beginner in python programming, how do you calculate the value of the one2many field? I have tried various kinds of references but still not resolved.

this is my code:

    parking_log_ids=fields.One2many('parking_log','parking_log_id',string='Log Parkir', ondelete='cascade')

class ParkingLog(models.Model):
    _name='parking_log'
    _rec_name='vehicle_id'
    

    vehicle_id=fields.Many2one('vehicle',string='Nomor Kendaraan')
    vehicle_type_id=fields.Char(string='Jenis Kendaraan', related='vehicle_id.vehicle_type.name')
    start_time=fields.Datetime(string='Masuk', default=fields.Datetime.now, required='True', readonly='True')
    end_time=fields.Datetime(string='Keluar' ,states={'in' : [('readonly', 'True')], 'paid' : [('readonly', 'True')]})
    rate_id=fields.Integer('Tarif / Jam', related='vehicle_id.vehicle_type.billing')

the value will always be updated as the value in the one2many field increases

and this is an image that shows the value that I will total (but in the picture the value is still 0) :
https://drive.google.com/file/d/1ecUEU9-UvyJcUdnzaXD5sHw7KrVkhZEq/view?usp=sharing

thank you in advance :D