from django.db import models

class Part(models.Model):

    name = models.CharField(max_length=20)

    class Meta:

        ordering = ("name",)

class Car(models.Model):

    name = models.CharField(max_length=20)

    default_parts = models.ManyToManyField(Part)

    optional_parts = models.ManyToManyField(Part, related_name="cars_optional")

    class Meta:

        ordering = ("name",)

class SportsCar(Car):

    price = models.IntegerField()

class Person(models.Model):

    name = models.CharField(max_length=20)

    fans = models.ManyToManyField("self", related_name="idols", symmetrical=False)

    friends = models.ManyToManyField("self")

    class Meta:

        ordering = ("name",)