code: from django.apps import AppConfig
  
  
  class ModelDefaultPKConfig(AppConfig):
      name = 'model_options'
  
  
  class ModelPKConfig(AppConfig):
      name = 'model_options'
      default_auto_field = 'django.db.models.SmallAutoField'
  
  
  class ModelPKNonAutoConfig(AppConfig):
      name = 'model_options'
      default_auto_field = 'django.db.models.TextField'
  
  
  class ModelPKNoneConfig(AppConfig):
      name = 'model_options'
      default_auto_field = None
  
  
  class ModelPKNonexistentConfig(AppConfig):
      name = 'model_options'
      default_auto_field = 'django.db.models.NonexistentAutoField'
  