code: def test_cov_mismatch():
      """Test estimation with MEG<->Head mismatch."""
      raw = read_raw_fif(raw_fname).crop(0, 5).load_data()
      events = find_events(raw, stim_channel="STI 014")
      raw.pick(raw.ch_names[:5])
      raw.add_proj([], remove_existing=True)
      epochs = Epochs(
          raw, events, None, tmin=-0.2, tmax=0.0, preload=True
      )
      for kind in ("shift", "None"):
          epochs_2 = epochs.copy()
          # This should be fine
          compute_covariance([epochs, epochs_2])
          if kind == "shift":
              epochs_2.info["dev_head_t"]["trans"][:3, 3] += 0.001
          else:  # None
              epochs_2.info["dev_head_t"] = None
          pytest.raises(
              ValueError, compute_covariance, [epochs, epochs_2]
          )
          compute_covariance([epochs, epochs_2], on_mismatch="ignore")
          with pytest.warns(RuntimeWarning, match="transform mismatch"):
              compute_covariance([epochs, epochs_2], on_mismatch="warn")
          with pytest.raises(ValueError, match="Invalid value"):
              compute_covariance(epochs, on_mismatch="x")
      # This should work
      epochs.info["dev_head_t"] = None
      epochs_2.info["dev_head_t"] = None
      compute_covariance([epochs, epochs_2], method=None)
  
imports: import itertools
  import sys
  from inspect import signature
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_almost_equal, assert_array_equal, assert_equal
  from mne import Epochs, compute_covariance, compute_proj_raw, compute_rank, compute_raw_covariance, create_info, find_events, make_ad_hoc_cov, make_fixed_length_events, merge_events, pick_channels_cov, pick_info, pick_types, read_cov, read_evokeds, write_cov
  from mne._fiff.pick import _DATA_CH_TYPES_SPLIT
  from mne.channels import equalize_channels
  from mne.cov import _auto_low_rank_model, _regularized_covariance, compute_whitener, prepare_noise_cov, regularize, whiten_evoked
  from mne.datasets import testing
  from mne.fixes import _safe_svd
  from mne.io import RawArray, read_info, read_raw_ctf, read_raw_fif
  from mne.preprocessing import maxwell_filter
  from mne.rank import _compute_rank_int
  from mne.utils import _record_warnings, assert_snr, catch_logging
label_desc: Use image node_id 2 for calling a global function with example usage: test_cov_mismatch() without return types