code: def test_make_inverse_operator_free(evoked, noise_cov):
      """Test MNE inverse computation (free orientation)."""
      fwd = read_forward_solution_meg(fname_fwd)
      fwd_surf = convert_forward_solution(fwd, surf_ori=True)
      fwd_fixed = convert_forward_solution(
          fwd, force_fixed=True, use_cps=True
      )
  
      # can't make free inv with fixed fwd
      with pytest.raises(ValueError, match="can only be used"):
          make_inverse_operator(
              evoked.info, fwd_fixed, noise_cov, depth=None
          )
  
      # for depth=None (or depth=0.8), surf_ori of the fwd should not matter
      inv_surf = make_inverse_operator(
          evoked.info, fwd_surf, noise_cov, depth=None, loose=1.0
      )
      inv = make_inverse_operator(
          evoked.info, fwd, noise_cov, depth=None, loose=1.0
      )
      assert "Free" in repr(inv_surf)
      assert "Free" in repr(inv)
      _compare_inverses_approx(
          inv,
          inv_surf,
          evoked,
          rtol=1e-5,
          atol=1e-8,
          check_nn=False,
          check_K=False,
      )
      for pick_ori in (None, "vector", "normal"):
          stc = apply_inverse(evoked, inv, pick_ori=pick_ori)
          stc_surf = apply_inverse(evoked, inv_surf, pick_ori=pick_ori)
          assert_allclose(stc_surf.data, stc.data, atol=1e-2)
  
imports: import copy
  import re
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_almost_equal, assert_array_equal, assert_array_less, assert_equal
  from scipy import sparse
  import mne
  from mne import Covariance, EvokedArray, SourceEstimate, combine_evoked, compute_raw_covariance, convert_forward_solution, make_ad_hoc_cov, make_forward_solution, make_sphere_model, pick_channels_forward, pick_types, pick_types_forward, read_cov, read_evokeds, read_forward_solution
  from mne.datasets import testing
  from mne.epochs import Epochs, EpochsArray, make_fixed_length_epochs
  from mne.event import read_events
  from mne.forward import apply_forward, is_fixed_orient, restrict_forward_to_stc
  from mne.io import read_info, read_raw_fif
  from mne.label import label_sign_flip, read_label
  from mne.minimum_norm import INVERSE_METHODS, apply_inverse, apply_inverse_cov, apply_inverse_epochs, apply_inverse_raw, apply_inverse_tfr_epochs, compute_rank_inverse, make_inverse_operator, prepare_inverse_operator, read_inverse_operator, write_inverse_operator
  from mne.source_estimate import VolSourceEstimate, read_source_estimate
  from mne.source_space._source_space import _get_src_nn
  from mne.surface import _normal_orth
  from mne.time_frequency import EpochsTFR
  from mne.utils import _record_warnings, catch_logging
label_desc: Use image node_id 20 for calling a global function with example usage: test_make_inverse_operator_free(evoked, noise_cov) without return types