title: How to programatically get manager instance for model in Django
body: <p>I have a custom manager added to model like that:</p>
  
  <pre><code>class StandardManagerModel(models.Model):
      pass
  
  class PublishableManager(models.Manager):
      pass
  
  class Publishable(models.Model):
      published_objects = PublishableManager()
  </code></pre>
  
  <p>This removes the default <code>.objects</code> manager from the model. How can i retrieve a default manager declared in model class? I would like a function like <code>get_default_manager()</code>:</p>
  
  <pre><code>manager = get_default_manager(Publishable)
  assert manager is Publishable.published_objects
  
  manager = get_default_manager(StandardManagerModel)
  assert manager is StandardManagerModel.objects
  </code></pre>