"""

DB-API Shortcuts

``get_object_or_404()`` is a shortcut function to be used in view functions for

performing a ``get()`` lookup and raising a ``Http404`` exception if a

``DoesNotExist`` exception was raised during the ``get()`` call.

``get_list_or_404()`` is a shortcut function to be used in view functions for

performing a ``filter()`` lookup and raising a ``Http404`` exception if a

``DoesNotExist`` exception was raised during the ``filter()`` call.

"""

from django.db import models

class Author(models.Model):

    name = models.CharField(max_length=50)

class ArticleManager(models.Manager):

    def get_queryset(self):

        return super().get_queryset().filter(authors__name__icontains="sir")

class AttributeErrorManager(models.Manager):

    def get_queryset(self):

        raise AttributeError("AttributeErrorManager")

class Article(models.Model):

    authors = models.ManyToManyField(Author)

    title = models.CharField(max_length=50)

    objects = models.Manager()

    by_a_sir = ArticleManager()

    attribute_error_objects = AttributeErrorManager()