old_contents: from django.db import models
  
  class AssetClass(models.Model):
      def __str__(self):
          return None
  
  class Portfolio(models.Model):
      name = models.CharField(max_length=128)
      objective = models.TextField()
      asset_classes = models.ManyToManyField(AssetClass)
      
      def __str__(self):
          return None
      
  class Security(models.Model):
      asset_class = models.ForeignKey(AssetClass)
      last_trade_price = models.DecimalField(max_digits=18, decimal_places=6)
      
      def __str__(self):
          return None
      
  class Account(models.Model):
      name = models.CharField(max_length=128)
      location = models.CharField(max_length=128)
      
      def __str__(self):
          return None
      
  class Transaction(models.Model):
      portfolio = models.ForeignKey(Portfolio)
      security = models.ForeignKey(Security)
      account = models.ForeignKey(Account)
      date = models.DateField()
      price = models.DecimalField(max_digits=18, decimal_places=6)
      quantity = models.SmallIntegerField()
  
      def __str__(self):
          return None
  
new_contents: from django.db import models
  
  class AssetClass(models.Model):
      name = models.CharField(max_length=128)
      def __str__(self):
          return self.name
  
  class Portfolio(models.Model):
      name = models.CharField(max_length=128)
      objective = models.TextField()
      asset_classes = models.ManyToManyField(AssetClass)
      
      def __str__(self):
          return self.name
      
  class Security(models.Model):
      name = models.CharField(max_length=128)
      asset_class = models.ForeignKey(AssetClass)
      last_trade_price = models.DecimalField(max_digits=18, decimal_places=6)
      
      def __str__(self):
          return self.name
      
  class Account(models.Model):
      name = models.CharField(max_length=128)
      location = models.CharField(max_length=128)
      
      def __str__(self):
          return self.name
      
  class Transaction(models.Model):
      portfolio = models.ForeignKey(Portfolio)
      security = models.ForeignKey(Security)
      account = models.ForeignKey(Account)
      date = models.DateField()
      price = models.DecimalField(max_digits=18, decimal_places=6)
      quantity = models.SmallIntegerField()
  
      def __str__(self):
          return self.date
  
subject: return name when __str__ is called