def root_node(self, tree_id):
        return self.get(**{
            self.tree_id_attr: tree_id,
            '%s__isnull' % self.parent_attr: True,
        })
Returns the root node of the tree with the given id.
dataset/ETHPy150Open agiliq/django-socialnews/socialnews/mptt/managers.py/TreeManager.root_node