code: def test_reciprocity_digraph(self):
      DG = nx.DiGraph([(1, 2), (2, 1)])
      reciprocity = nx.reciprocity(DG)
      assert reciprocity == 1.0
  
file_path: networkx/networkx/algorithms/tests/test_reciprocity.py
imports: import pytest
  import networkx
label_desc: Use image node_id 1 for calling the TestReciprocity obj's underlying member method code with example usage: obj.test_reciprocity_digraph() without return types