code: def test_edf_prefilter_parse():
      """Test prefilter strings from header are parsed correctly."""
      prefilter_basic = ["HP: 0Hz LP: 0Hz"]
      highpass, lowpass = _parse_prefilter_string(prefilter_basic)
      assert_array_equal(highpass, ["0"])
      assert_array_equal(lowpass, ["0"])
  
      prefilter_normal_multi_ch = ["HP: 1Hz LP: 30Hz"] * 10
      highpass, lowpass = _parse_prefilter_string(
          prefilter_normal_multi_ch
      )
      assert_array_equal(highpass, ["1"] * 10)
      assert_array_equal(lowpass, ["30"] * 10)
  
      prefilter_unfiltered_ch = prefilter_normal_multi_ch + [""]
      highpass, lowpass = _parse_prefilter_string(
          prefilter_unfiltered_ch
      )
      assert_array_equal(highpass, ["1"] * 10)
      assert_array_equal(lowpass, ["30"] * 10)
  
      prefilter_edf_specs_doc = ["HP:0.1Hz LP:75Hz N:50Hz"]
      highpass, lowpass = _parse_prefilter_string(
          prefilter_edf_specs_doc
      )
      assert_array_equal(highpass, ["0.1"])
      assert_array_equal(lowpass, ["75"])
  
imports: import datetime
  from contextlib import nullcontext
  from functools import partial
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_almost_equal, assert_array_equal, assert_equal
  from scipy.io import loadmat
  from mne import Annotations, pick_types
  from mne._fiff.pick import channel_indices_by_type, get_channel_type_constants
  from mne.annotations import _ndarray_ch_names, events_from_annotations, read_annotations
  from mne.datasets import testing
  from mne.io import edf, read_raw_bdf, read_raw_edf, read_raw_fif, read_raw_gdf
  from mne.io.edf.edf import _edf_str, _parse_prefilter_string, _read_annotations_edf, _read_ch, _read_edf_header, _read_header
  from mne.io.tests.test_raw import _test_raw_reader
  from mne.tests.test_annotations import _assert_annotations_equal
label_desc: Use image node_id 21 for calling a global function with example usage: test_edf_prefilter_parse() without return types