code: def test_zinc():
      mode_n_graphs = {
          "train": 10000,
          "valid": 1000,
          "test": 1000,
      }
      transform = dgl.AddSelfLoop(allow_duplicate=True)
      for mode, n_graphs in mode_n_graphs.items():
          dataset1 = data.ZINCDataset(mode=mode)
          g1, label = dataset1[0]
          dataset2 = data.ZINCDataset(mode=mode, transform=transform)
          g2, _ = dataset2[0]
  
          assert g2.num_edges() - g1.num_edges() == g1.num_nodes()
          # return a scalar tensor
          assert not label.shape
  
imports: import gzip
  import io
  import os
  import tarfile
  import tempfile
  import unittest
  import warnings
  import backend
  import dgl
  import dgl.data
  import numpy
  import pandas
  import pytest
  import yaml
  from dgl import DGLError
label_desc: Use image node_id 14 for calling a global function with example usage: test_zinc() without return types