code: def test_has_successor(self):
      G = self.K3
      assert G.has_successor(0, 1)
      assert not G.has_successor(0, -1)
  
imports: import pytest
  import networkx
  from networkx.utils import nodes_equal
  from .test_graph import BaseAttrGraphTester, BaseGraphTester
  from .test_graph import TestEdgeSubgraph
  from .test_graph import TestGraph
label_desc: Use image node_id 1 for calling the BaseDiGraphTester obj's underlying member method code with example usage: obj.test_has_successor() without return types