code: def test_total_num_graph(self):
      self.assertEqual(self._reader.total_num_graphs, 1)
  
file_path: jraph/jraph/ogb_examples/data_utils_test.py
imports: import pathlib
  from absl.testing import absltest
  from absl.testing import parameterized
  import jraph
  from jraph.ogb_examples import data_utils
  import numpy
  import tree
label_desc: Use image node_id 2 for calling the DataUtilsTest obj's underlying member method code with example usage: obj.test_total_num_graph() without return types