old_contents: # -*- coding: utf-8
  from __future__ import unicode_literals
  from django.db import models
  from django.utils.encoding import python_2_unicode_compatible
  
  
  @python_2_unicode_compatible
  class Knight(models.Model):
      name = models.CharField(max_length=63)
      traitor = models.BooleanField()
  
      def __str__(self):
          return self.name
  
new_contents: # -*- coding: utf-8
  from __future__ import unicode_literals
  from django.db import models
  from django.utils.encoding import python_2_unicode_compatible
  
  
  @python_2_unicode_compatible
  class Knight(models.Model):
      name = models.CharField(max_length=63)
      traitor = models.BooleanField(default=False)
  
      def __str__(self):
          return self.name
  
subject: Add False default to traitor BooleanField.