code: def test_maxfilter_io():
      """Test maxfilter io."""
      info = read_info(raw_fname)
      mf = info["proc_history"][1]["max_info"]
  
      assert mf["sss_info"]["frame"] == FIFF.FIFFV_COORD_HEAD
      # based on manual 2.0, rev. 5.0 page 23
      assert 5 <= mf["sss_info"]["in_order"] <= 11
      assert mf["sss_info"]["out_order"] <= 5
      assert mf["sss_info"]["nchan"] > len(mf["sss_info"]["components"])
  
      assert (
          info["ch_names"][: mf["sss_info"]["nchan"]]
          == mf["sss_ctc"]["proj_items_chs"]
      )
      assert mf["sss_ctc"]["decoupler"].shape == (
          mf["sss_info"]["nchan"],
          mf["sss_info"]["nchan"],
      )
      assert_array_equal(
          np.unique(np.diag(mf["sss_ctc"]["decoupler"].toarray())),
          np.array([1.0], dtype=np.float32),
      )
      assert mf["sss_cal"]["cal_corrs"].shape == (306, 14)
      assert mf["sss_cal"]["cal_chans"].shape == (306, 2)
      vv_coils = [v for k, v in FIFF.items() if "FIFFV_COIL_VV" in k]
      assert all(
          k in vv_coils for k in set(mf["sss_cal"]["cal_chans"][:, 1])
      )
  
imports: from pathlib import Path
  import numpy
  from numpy.testing import assert_array_equal
  from mne._fiff.constants import FIFF
  from mne.io import read_info
label_desc: Use image node_id 1 for calling a global function with example usage: test_maxfilter_io() without return types