code: def test_GNN_node_masking():
      """Tests the unsupervised node masking task"""
      from deepchem.models.torch_models.gnn import GNNModular
  
      dataset, _ = get_regression_dataset()
      model = GNNModular(task="mask_nodes", device="cpu")
      loss1 = model.fit(dataset, nb_epoch=5)
      loss2 = model.fit(dataset, nb_epoch=5)
      assert loss2 < loss1
  
file_path: deepchem/deepchem/models/tests/test_gnn.py
imports: import os
  import pytest
  import numpy
  import deepchem
  from deepchem.feat.molecule_featurizers import SNAPFeaturizer
label_desc: Use image node_id 8 for calling a global function with example usage: test_GNN_node_masking() without return types