code: def test_tuplelabels(self, stringizer):
      # https://github.com/networkx/networkx/pull/1048
      # Writing tuple labels to GML failed.
      G = nx.Graph()
      G.add_edge((0, 1), (1, 0))
      data = "\n".join(nx.generate_gml(G, stringizer=stringizer))
      answer = """graph [
    node [
      id 0
      label "(0,1)"
    ]
    node [
      id 1
      label "(1,0)"
    ]
    edge [
      source 0
      target 1
    ]
  ]"""
      assert data == answer
  
imports: import codecs
  import io
  import math
  from ast import literal_eval
  from contextlib import contextmanager
  from textwrap import dedent
  import pytest
  import networkx
  from networkx.readwrite.gml import literal_destringizer, literal_stringizer
label_desc: Use image node_id 7 for calling the TestGraph obj's underlying member method code with example usage: obj.test_tuplelabels(stringizer) without return types