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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_queryset(self, request):
 """ Returns a QuerySet of all model instances that can be edited by the admin site. This is used by changelist_view. """

        qs = self.model._default_manager.get_queryset()
        qs.__class__ = TreeEditorQuerySet
        return qs