'Returns a new QuerySet instance that will prefetch the specified
Many-To-One and Many-To-Many related objects when the QuerySet is
evaluated.
When prefetch_related() is called more than once, the list of lookups to
prefetch is appended to. If prefetch_related(None) is called, the
the list is cleared.'

def prefetch_related(self, *lookups):

    clone = self._clone()
    if (lookups == (None,)):
        clone._prefetch_related_lookups = []
    else:
        clone._prefetch_related_lookups.extend(lookups)
    return clone
