old_contents: from django.db import models
  
  # Create your models here.
  
  class Person(AmadaaModel):
      first_name = models.CharField(max_length=50)
      last_name = models.CharField(max_length=50)
      
      def __str__(self):
          return "{} {}".format(self.first_name, self.last_name)
  
  class Organization(AmadaaModel):
      name = models.CharField(max_length=100)
      members = models.ManyToManyField(
              Person,
              through='Membership',
              through_fields=('organization', 'person'))
  
      def __str__(self):
          return "{}".format(self.name)
  
  class Membership(AmadaaModel):
      organization = models.ForeignKey(Organization)
      person = models.ForeignKey(Person)
  
      def __str__(self):
          return "{} member of {}".format(self.person, self.organization)
  
new_contents: from django.db import models
  from amadaa.models import AmadaaModel
  
  # Create your models here.
  
  class Person(AmadaaModel):
      first_name = models.CharField(max_length=50)
      last_name = models.CharField(max_length=50)
      
      def __str__(self):
          return "{} {}".format(self.first_name, self.last_name)
  
  class Organization(AmadaaModel):
      name = models.CharField(max_length=100)
      members = models.ManyToManyField(
              Person,
              through='Membership',
              through_fields=('organization', 'person'))
  
      def __str__(self):
          return "{}".format(self.name)
  
  class Membership(AmadaaModel):
      organization = models.ForeignKey(Organization)
      person = models.ForeignKey(Person)
  
      def __str__(self):
          return "{} member of {}".format(self.person, self.organization)
  
subject: Fix missing import.