code: def test_make_forward_solution_bti(fname_src_small):
      """Test BTI end-to-end versus C."""
      bti_pdf = bti_dir / "test_pdf_linux"
      bti_config = bti_dir / "test_config_linux"
      bti_hs = bti_dir / "test_hs_linux"
      fname_bti_raw = bti_dir / "exported4D_linux_raw.fif"
      raw_py = read_raw_bti(bti_pdf, bti_config, bti_hs, preload=False)
      src = read_source_spaces(fname_src_small)
      fwd_py = make_forward_solution(
          raw_py.info,
          src=src,
          eeg=False,
          meg=True,
          bem=fname_bem_meg,
          trans=trans_path,
      )
      fwd = _do_forward_solution(
          "sample",
          fname_bti_raw,
          src=fname_src_small,
          bem=fname_bem_meg,
          mri=trans_path,
          eeg=False,
          meg=True,
          subjects_dir=subjects_dir,
      )
      _compare_forwards(fwd, fwd_py, 248, n_src_small)
  
imports: from itertools import product
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_equal, assert_array_less
  from mne import convert_forward_solution, create_info, get_volume_labels_from_aseg, make_forward_solution, make_sphere_model, pick_info, pick_types, pick_types_forward, read_cov, read_dipole, read_evokeds, read_forward_solution, read_source_spaces, setup_volume_source_space, write_forward_solution
  from mne._fiff.constants import FIFF
  from mne.bem import make_bem_solution, read_bem_surfaces
  from mne.channels import make_standard_montage
  from mne.datasets import testing
  from mne.dipole import Dipole, fit_dipole
  from mne.forward import Forward, _do_forward_solution, use_coil_def
  from mne.forward._compute_forward import _magnetic_dipole_field_vec
  from mne.forward._make_forward import _create_meg_coils, make_forward_dipole
  from mne.forward.tests.test_forward import assert_forward_allclose
  from mne.io import read_info, read_raw_bti, read_raw_fif, read_raw_kit
  from mne.simulation import simulate_evoked
  from mne.source_estimate import VolSourceEstimate
  from mne.source_space._source_space import _compare_source_spaces, setup_source_space, write_source_spaces
  from mne.surface import _get_ico_surface
  from mne.transforms import Transform
  from mne.utils import catch_logging, requires_mne, requires_mne_mark, requires_openmeeg_mark, run_subprocess
label_desc: Use image node_id 6 for calling a global function with example usage: test_make_forward_solution_bti(fname_src_small) without return types