code: def test_one_channel_gdf():
      """Test a one-channel GDF file."""
      with pytest.warns(RuntimeWarning, match="different highpass"):
          ecg = read_raw_gdf(gdf_1ch_path, preload=True)
      assert ecg["ECG"][0].shape == (1, 4500)
      assert 150.0 == ecg.info["sfreq"]
  
file_path: mne-python/mne/io/edf/tests/test_gdf.py
imports: import shutil
  from datetime import datetime, timedelta, timezone
  import numpy
  import pytest
  import scipy.io
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_equal
  from mne import events_from_annotations, find_events, pick_types
  from mne.datasets import testing
  from mne.io import read_raw_gdf
  from mne.io.tests.test_raw import _test_raw_reader
label_desc: Use image node_id 4 for calling a global function with example usage: test_one_channel_gdf() without return types