code: def test_csd_epochs(tmp_path):
      """Test making epochs, saving to disk and loading."""
      raw = read_raw_fif(raw_fname)
      raw.pick(picks=["eeg", "stim"]).load_data()
      events = find_events(raw)
      epochs = Epochs(raw, events, reject=dict(eeg=1e-4), preload=True)
      epochs = compute_current_source_density(epochs)
      epo_fname = tmp_path / "test_csd_epo.fif"
      epochs.save(epo_fname)
      epochs2 = read_epochs(epo_fname, preload=True)
      assert_allclose(epochs._data, epochs2._data)
  
file_path: mne-python/mne/preprocessing/tests/test_csd.py
imports: from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose
  from scipy import linalg
  from scipy.io import loadmat
  from mne import Epochs, EvokedArray, create_info, find_events, pick_types, read_epochs
  from mne._fiff.constants import FIFF
  from mne.channels import make_dig_montage
  from mne.datasets import testing
  from mne.io import RawArray, read_raw_fif
  from mne.preprocessing import compute_bridged_electrodes, compute_current_source_density
  from mne.utils import object_diff
label_desc: Use image node_id 5 for calling a global function with example usage: test_csd_epochs(tmp_path) without return types