Django ModelForm Validierung mit clean() Methode

from django import forms
from .models import Product
 
class ProductForm(forms.ModelForm):
    class Meta:
        model = Product
        fields = ['name', 'price', 'stock']
 
    
    def clean(self):
        cleaned_data = super().clean()
        price = cleaned_data.get('price')
        stock = cleaned_data.get('stock')
        if price and price < 0:
            raise forms.ValidationError('Price cannot be negative')
        if stock is not None and stock < 0:
            raise forms.ValidationError('Stock cannot be negative')
        if price and stock and price * stock > 1000000:
            raise forms.ValidationError('Inventory value exceeds limit')
        return cleaned_data