code: def test_amazon_ratings():
      transform = dgl.AddSelfLoop(allow_duplicate=True)
  
      g = dgl.data.AmazonRatingsDataset(force_reload=True)[0]
      assert g.num_nodes() == 24492
      assert g.num_edges() == 186100
      g2 = dgl.data.AmazonRatingsDataset(
          force_reload=True, transform=transform
      )[0]
      assert g2.num_edges() - g.num_edges() == g.num_nodes()
  
file_path: dgl/tests/python/common/data/data/test_heterophilous_graphs.py
imports: import unittest
  import backend
  import dgl
label_desc: Use image node_id 2 for calling a global function with example usage: test_amazon_ratings() without return types