code: def test_evoked_detrend():
      """Test for detrending evoked data."""
      ave = read_evokeds(fname, 0)
      ave_normal = read_evokeds(fname, 0)
      ave.detrend(0)
      ave_normal.data -= np.mean(ave_normal.data, axis=1)[:, np.newaxis]
      picks = pick_types(ave.info, meg=True, eeg=True, exclude="bads")
      assert_allclose(
          ave.data[picks], ave_normal.data[picks], rtol=1e-8, atol=1e-16
      )
  
imports: import pickle
  from copy import deepcopy
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_almost_equal, assert_array_equal, assert_equal
  from scipy import fftpack
  from mne import Epochs, EpochsArray, combine_evoked, create_info, equalize_channels, pick_types, read_events, read_evokeds, write_evokeds
  from mne._fiff.constants import FIFF
  from mne.evoked import Evoked, EvokedArray, _get_peak
  from mne.io import read_raw_fif
  from mne.utils import grand_average
label_desc: Use image node_id 13 for calling a global function with example usage: test_evoked_detrend() without return types