Add new QuerySet methods using a Model inner class

managers.py

from django.db import models

class QuerySetManager(models.Manager):
  """Add new QuerySet methods using a Model inner class

  Reference:
    http://djangosnippets.org/snippets/734/

  """

  def __getattr__(self, name, *args):
    if name.startswith('_'):
      raise AttributeError
    return getattr(self.get_query_set(), name, *args)

  def get_query_set(self):
    return self.model.QuerySet(self.model)