code: def test_reader(dataset):
      # defaults to using cudf
      E = dataset.get_edgelist(download=True)
  
      assert E is not None
      assert isinstance(E, cudf.core.dataframe.DataFrame)
      dataset.unload()
  
      # using pandas
      E_pd = dataset.get_edgelist(download=True, reader="pandas")
  
      assert E_pd is not None
      assert isinstance(E_pd, pandas.core.frame.DataFrame)
      dataset.unload()
  
      with pytest.raises(ValueError):
          dataset.get_edgelist(reader="fail")
          dataset.get_edgelist(reader=None)
  
imports: import os
  import gc
  from pathlib import Path
  from tempfile import TemporaryDirectory
  import pandas
  import pytest
  import cudf
  import dask_cudf
  from cugraph.structure import Graph
  from cugraph.testing import RAPIDS_DATASET_ROOT_DIR_PATH, ALL_DATASETS, WEIGHTED_DATASETS, SMALL_DATASETS, BENCHMARKING_DATASETS
  from cugraph import datasets
  from cugraph.dask.common.mg_utils import is_single_gpu
label_desc: Use image node_id 10 for calling a global function with example usage: test_reader(dataset) without return types