code: def test_overall_reciprocity_empty_graph(self):
      with pytest.raises(nx.NetworkXError):
          DG = nx.DiGraph()
          nx.overall_reciprocity(DG)
  
file_path: networkx/networkx/algorithms/tests/test_reciprocity.py
imports: import pytest
  import networkx
label_desc: Use image node_id 2 for calling the TestReciprocity obj's underlying member method code with example usage: obj.test_overall_reciprocity_empty_graph() without return types