code: def three_chanpos_fname(tmp_path_factory):
      """Test file with 3 channels to exercise EEGLAB reader.
  
      File characteristics
         - ch_names: 'F3', 'unknown', 'FPz'
         - 'FPz' has no position information.
         - the rest is aleatory
  
      Notes from when this code was factorized:
      # test reading file with one event (read old version)
      """
      fname = str(tmp_path_factory.mktemp("data") / "test_chanpos.set")
      file_conent = dict(
          EEG={
              "trials": 1,
              "nbchan": 3,
              "pnts": 3,
              "epoch": [],
              "event": [],
              "srate": 128,
              "times": np.array([0.0, 0.1, 0.2]),
              "data": np.empty([3, 3]),
              "chanlocs": np.array(
                  [
                      (b"F3", 1.0, 4.0, 7.0),
                      (b"unknown", np.nan, np.nan, np.nan),
                      (b"FPz", 2.0, 5.0, 8.0),
                  ],
                  dtype=[
                      ("labels", "S10"),
                      ("X", "f8"),
                      ("Y", "f8"),
                      ("Z", "f8"),
                  ],
              ),
          }
      )
  
      io.savemat(
          file_name=fname,
          mdict=file_conent,
          appendmat=False,
          oned_as="row",
      )
  
      return fname
  
imports: import os
  import shutil
  from copy import deepcopy
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_almost_equal, assert_array_equal, assert_equal
  from scipy import io
  import mne
  from mne import read_epochs_eeglab, write_events
  from mne.annotations import events_from_annotations, read_annotations
  from mne.channels import read_custom_montage
  from mne.datasets import testing
  from mne.io import read_raw_eeglab
  from mne.io.eeglab._eeglab import _readmat
  from mne.io.eeglab.eeglab import _dol_to_lod, _get_montage_information
  from mne.io.tests.test_raw import _test_raw_reader
  from mne.utils import Bunch, _check_pymatreader_installed
label_desc: Use image node_id 10 for calling a global function with example usage: three_chanpos_fname(tmp_path_factory) and returns: fname