old_contents: from django.db import models
  from django.conf import settings
  
  
  class Note(models.Model):
      user = models.ForeignKey(
          settings.AUTH_USER_MODEL, blank=True, null=True,
          on_delete=models.SET_NULL)
      date = models.DateTimeField(db_index=True, auto_now_add=True)
      content = models.TextField()
      is_public = models.BooleanField(default=True)
  
      class Meta:
          ordering = ('date', )
  
new_contents: from django.conf import settings
  from django.db import models
  
  
  class Note(models.Model):
      user = models.ForeignKey(
          settings.AUTH_USER_MODEL, blank=True, null=True,
          on_delete=models.SET_NULL)
      date = models.DateTimeField(db_index=True, auto_now_add=True)
      content = models.TextField()
      is_public = models.BooleanField(default=True)
  
      class Meta:
          ordering = ('date', )
  
subject: Fix imports