class Project(models.Model):
    class Customer(models.Model):
        customer_id = models.IntegerField(default=0)
        customer_name = models.CharField(max_length=200)
        def __str__(self):
            return self.customer_name
    
    class Account(models.Model):
        account_id = models.IntegerField(default=0)
        customer = models.ForeignKey(Customer, on_delete=models.CASCADE)
        description = models.CharField(max_length=200)
        limit = models.IntegerField(default=0)

        def __str__(self):
            return self.description