How can I read child model class' DecimalField attribute 'decimal_places' from inside a parent Meta class

Hello.

I have a parent Meta class and some child classes.

I would like to read the decimal_places attribute from DecimalField of my child instances using a function in my parent class.

I am able to read the attribute from inside my child classes, but I cant crack how to read from a function in the parent class.

Using @classmethod I get one error, not using it, I get another (see comments in the condensed example code below).

I'm presently learning Python and Django, so please feel free to educate me a bit here :)

thanks, Mikkel

from django.db import models
from django.shortcuts import render

class Vehicles(models.Model):
   
    speed = models.DecimalField(max_digits=5, decimal_places=2)
   
    @classmethod
    def get_speed_decimal_places(self):
# @classmethod:     Will raise 'DeferredAttribute' object has no attribute 'decimal_places'
# no classmethod:   Will raise 'NoneType' object has no attribute 'decimal_places'
        return self.speed.decimal_places
   
    class Meta:
        abstract = True

class Train(Vehicles):
    speed = models.DecimalField(max_digits=5, decimal_places=2)
    train_speed_decimals = speed.decimal_places
   
class Aeroplane(Vehicles):
    speed = models.DecimalField(max_digits=5, decimal_places=1)
    aeroplane_speed_decimals = speed.decimal_places
   
def SpeedView(request):
    t = Train()
    context = {}
    # This works just fine
    context['decimals_own'] = t.train_speed_decimals
    # This raises error in get_speed_decimal_places()
    context['decimals_cls'] = t.get_speed_decimal_places()
   
    return render(request,'speed_index.html',context)

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