code: def test_predecessors(self):
      G = self.K3
      assert sorted(G.predecessors(0)) == [1, 2]
      with pytest.raises(nx.NetworkXError):
          G.predecessors(-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 4 for calling the BaseDiGraphTester obj's underlying member method code with example usage: obj.test_predecessors() without return types