':returns: A queryset of all the node\'s descendants as DFS, doesn\'t
include the node itself'

def get_descendants(self, include_self=False):

    if include_self:
        return self.__class__.get_tree(self).filter(site_id=self.site_id)
    else:
        return self.__class__.get_tree(self).exclude(pk=self.pk).filter(site_id=self.site_id)
