text: """
  Giving models a custom manager
  
  You can use a custom ``Manager`` in a particular model by extending the base
  ``Manager`` class and instantiating your custom ``Manager`` in your model.
  
  There are two reasons you might want to customize a ``Manager``: to add extra
  ``Manager`` methods, and/or to modify the initial ``QuerySet`` the ``Manager``
  returns.
  """
  
  from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
  from django.db import models
  
  
  class PersonManager(models.Manager):
      def get_fun_people(self):
          return self.filter(fun=True)
  
  
  class PublishedBookManager(models.Manager):
      def get_queryset(self):
          return super().get_queryset().filter(is_published=True)
  
  
  class AnnotatedBookManager(models.Manager):
      def get_queryset(self):
          return (
              super()
              .get_queryset()
              .annotate(favorite_avg=models.Avg("favorite_books__favorite_thing_id"))
          )
  
  
  class CustomQuerySet(models.QuerySet):
      def filter(self, *args, **kwargs):
          queryset = super().filter(fun=True)
          queryset._filter_CustomQuerySet = True
          return queryset
  
      def public_method(self, *args, **kwargs):
          return self.all()
  
      def _private_method(self, *args, **kwargs):
          return self.all()
  
      def optout_public_method(self, *args, **kwargs):
          return self.all()
  
      optout_public_method.queryset_only = True
  
      def _optin_private_method(self, *args, **kwargs):
          return self.all()
  
      _optin_private_method.queryset_only = False
  
  
  class BaseCustomManager(models.Manager):
      def __init__(self, arg):
          super().__init__()
          self.init_arg = arg
  
      def filter(self, *args, **kwargs):
          queryset = super().filter(fun=True)
          queryset._filter_CustomManager = True
          return queryset
  
      def manager_only(self):
          return self.all()
  
  
  CustomManager = BaseCustomManager.from_queryset(CustomQuerySet)
  
  
  class CustomInitQuerySet(models.QuerySet):
      # QuerySet with an __init__() method that takes an additional argument.
      def __init__(
          self, custom_optional_arg=None, model=None, query=None, using=None, hints=None
      ):
          super().__init__(model=model, query=query, using=using, hints=hints)
  
  
  class DeconstructibleCustomManager(BaseCustomManager.from_queryset(CustomQuerySet)):
      def __init__(self, a, b, c=1, d=2):
          super().__init__(a)
  
  
  class FunPeopleManager(models.Manager):
      def get_queryset(self):
          return super().get_queryset().filter(fun=True)
  
  
  class BoringPeopleManager(models.Manager):
      def get_queryset(self):
          return super().get_queryset().filter(fun=False)
  
  
  class Person(models.Model):
      first_name = models.CharField(max_length=30)
      last_name = models.CharField(max_length=30)
      fun = models.BooleanField(default=False)
  
      favorite_book = models.ForeignKey(
          "Book", models.SET_NULL, null=True, related_name="favorite_books"
      )
      favorite_thing_type = models.ForeignKey(
          "contenttypes.ContentType", models.SET_NULL, null=True
      )
      favorite_thing_id = models.IntegerField(null=True)
      favorite_thing = GenericForeignKey("favorite_thing_type", "favorite_thing_id")
  
      objects = PersonManager()
      fun_people = FunPeopleManager()
      boring_people = BoringPeopleManager()
  
      custom_queryset_default_manager = CustomQuerySet.as_manager()
      custom_queryset_custom_manager = CustomManager("hello")
      custom_init_queryset_manager = CustomInitQuerySet.as_manager()
  
      def __str__(self):
          return "%s %s" % (self.first_name, self.last_name)
  
  
  class FunPerson(models.Model):
      first_name = models.CharField(max_length=30)
      last_name = models.CharField(max_length=30)
      fun = models.BooleanField(default=True)
      favorite_book = models.ForeignKey(
          "Book",
          models.SET_NULL,
          null=True,
          related_name="fun_people_favorite_books",
      )
      favorite_thing_type = models.ForeignKey(
          "contenttypes.ContentType", models.SET_NULL, null=True
      )
      favorite_thing_id = models.IntegerField(null=True)
      favorite_thing = GenericForeignKey("favorite_thing_type", "favorite_thing_id")
  
      objects = FunPeopleManager()
  
  
  class Book(models.Model):
      title = models.CharField(max_length=50)
      author = models.CharField(max_length=30)
      is_published = models.BooleanField(default=False)
      authors = models.ManyToManyField(Person, related_name="books")
      fun_authors = models.ManyToManyField(FunPerson, related_name="books")
      favorite_things = GenericRelation(
          Person,
          content_type_field="favorite_thing_type",
          object_id_field="favorite_thing_id",
      )
      fun_people_favorite_things = GenericRelation(
          FunPerson,
          content_type_field="favorite_thing_type",
          object_id_field="favorite_thing_id",
      )
  
      published_objects = PublishedBookManager()
      annotated_objects = AnnotatedBookManager()
  
      class Meta:
          base_manager_name = "annotated_objects"
  
  
  class ConfusedBook(models.Model):
      title = models.CharField(max_length=50)
      author = models.CharField(max_length=30)
      favorite_things = GenericRelation(
          Person,
          content_type_field="favorite_thing_type",
          object_id_field="favorite_thing_id",
      )
      less_favorite_things = GenericRelation(
          FunPerson,
          content_type_field="favorite_thing_type",
          object_id_field="favorite_thing_id",
          related_query_name="favorite_things",
      )
  
  
  class FastCarManager(models.Manager):
      def get_queryset(self):
          return super().get_queryset().filter(top_speed__gt=150)
  
  
  class Car(models.Model):
      name = models.CharField(max_length=10)
      mileage = models.IntegerField()
      top_speed = models.IntegerField(help_text="In miles per hour.")
      cars = models.Manager()
      fast_cars = FastCarManager()
  
  
  class FastCarAsBase(Car):
      class Meta:
          proxy = True
          base_manager_name = "fast_cars"
  
  
  class FastCarAsDefault(Car):
      class Meta:
          proxy = True
          default_manager_name = "fast_cars"
  
  
  class RestrictedManager(models.Manager):
      def get_queryset(self):
          return super().get_queryset().filter(is_public=True)
  
  
  class RelatedModel(models.Model):
      name = models.CharField(max_length=50)
  
  
  class RestrictedModel(models.Model):
      name = models.CharField(max_length=50)
      is_public = models.BooleanField(default=False)
      related = models.ForeignKey(RelatedModel, models.CASCADE)
  
      objects = RestrictedManager()
      plain_manager = models.Manager()
  
  
  class OneToOneRestrictedModel(models.Model):
      name = models.CharField(max_length=50)
      is_public = models.BooleanField(default=False)
      related = models.OneToOneField(RelatedModel, models.CASCADE)
  
      objects = RestrictedManager()
      plain_manager = models.Manager()
  
  
  class AbstractPerson(models.Model):
      abstract_persons = models.Manager()
      objects = models.CharField(max_length=30)
  
      class Meta:
          abstract = True
  
  
  class PersonFromAbstract(AbstractPerson):
      pass
  