little fix

  dataset_file = os.path.join(

      current_dir, "./gdb7.sdf")

  gdb7_tasks = ["u0_atom"]

  if featurizer == None:

    featurizer = dc.feat.CoulombMatrix(23)

  if featurizer is None:

    featurizer = dc.feat.CoulombMatrixEig(23)

  loader = dc.data.SDFLoader(tasks=gdb7_tasks, smiles_filed="smiles", 

                             mol_field="mol", featurizer=featurizer)

  dataset = loader.featurize(dataset_file)