code: def test_orig_units(recwarn):
      """Test exposure of original channel units."""
      raw = read_raw_brainvision(vhdr_path)
      orig_units = raw._orig_units
      assert len(orig_units) == 32
      assert orig_units["FP1"] == "µV"
  
      # no unit specified in the vhdr, ensure we default to µV here
      assert orig_units["FP2"] == "µV"
      assert orig_units["F3"] == "µV"
  
      sum([v == "µV" for v in orig_units.values()]) == 26
  
      assert (
          orig_units["CP5"] == "n/a"
      )  # originally BS, not a valid unit
      assert orig_units["CP6"] == "µS"
      assert (
          orig_units["HL"] == "n/a"
      )  # originally ARU, not a valid unit
      assert orig_units["HR"] == "n/a"  # originally uS ...
      assert orig_units["Vb"] == "S"
      assert orig_units["ReRef"] == "C"
  
imports: import datetime
  import re
  import shutil
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_equal
  from mne import concatenate_raws, pick_types, read_annotations
  from mne._fiff.constants import FIFF
  from mne.annotations import events_from_annotations
  from mne.datasets import testing
  from mne.io import read_raw_brainvision, read_raw_fif
  from mne.io.tests.test_raw import _test_raw_reader
  from mne.utils import _stamp_to_dt, object_diff
label_desc: Use image node_id 1 for calling a global function with example usage: test_orig_units(recwarn) without return types