code: def test_has_successor(self):
      G = self.K3
      assert G.has_successor(0, 1)
      assert not G.has_successor(0, -1)
  
imports: from collections import UserDict
  import pytest
  import networkx
  from networkx.utils import edges_equal
  from .test_multigraph import BaseMultiGraphTester
  from .test_multigraph import TestEdgeSubgraph
  from .test_multigraph import TestMultiGraph
label_desc: Use image node_id 13 for calling the BaseMultiDiGraphTester obj's underlying member method code with example usage: obj.test_has_successor() without return types