code: def test_successors(self):
      G = self.K3
      assert sorted(G.successors(0)) == [1, 2]
      pytest.raises((KeyError, nx.NetworkXError), G.successors, -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 14 for calling the BaseMultiDiGraphTester obj's underlying member method code with example usage: obj.test_successors() without return types