from django.db import models

class Account(models.Model):

    num = models.IntegerField()

class Person(models.Model):

    GENDER_CHOICES = (

        ("M", "Male"),

        ("F", "Female"),

    )

    name = models.CharField(max_length=20)

    gender = models.CharField(max_length=1, choices=GENDER_CHOICES)

    pid = models.IntegerField(null=True, default=None)

class Employee(Person):

    employee_num = models.IntegerField(default=0)

    profile = models.ForeignKey(

        "Profile", models.SET_NULL, related_name="profiles", null=True

    )

    accounts = models.ManyToManyField("Account", related_name="employees", blank=True)

class NonConcreteField(models.IntegerField):

    def db_type(self, connection):

        return None

    def get_attname_column(self):

        attname, _ = super().get_attname_column()

        return attname, None

class Profile(models.Model):

    name = models.CharField(max_length=200)

    salary = models.FloatField(default=1000.0)

    non_concrete = NonConcreteField()

class ProxyEmployee(Employee):

    class Meta:

        proxy = True