code: def test_drop_channels():
      """Test if dropping channels works with various arguments."""
      raw = read_raw_fif(raw_fname).crop(0, 0.1)
      raw.drop_channels(["MEG 0111"])  # list argument
      raw.drop_channels("MEG 0112")  # str argument
      raw.drop_channels({"MEG 0132", "MEG 0133"})  # set argument
      pytest.raises(ValueError, raw.drop_channels, ["MEG 0111", 5])
      pytest.raises(
          ValueError, raw.drop_channels, 5
      )  # must be list or str
  
      # by default, drop channels raises a ValueError if a channel can't be found
      m_chs = ["MEG 0111", "MEG blahblah"]
      with pytest.raises(
          ValueError, match="not found, nothing dropped"
      ):
          raw.drop_channels(m_chs)
      # ...but this can be turned to a warning
      with pytest.warns(
          RuntimeWarning, match="not found, nothing dropped"
      ):
          raw.drop_channels(m_chs, on_missing="warn")
      # ...or ignored altogether
      raw.drop_channels(m_chs, on_missing="ignore")
  
imports: import hashlib
  from copy import deepcopy
  from functools import partial
  from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_equal, assert_equal
  from scipy.io import savemat
  from mne import Epochs, EpochsArray, EvokedArray, create_info, make_ad_hoc_cov, pick_channels, pick_types, read_events
  from mne._fiff.constants import FIFF, _ch_unit_mul_named
  from mne.channels import combine_channels, equalize_channels, find_ch_adjacency, get_builtin_ch_adjacencies, make_1020_channel_selections, read_ch_adjacency, read_custom_montage, rename_channels
  from mne.channels.channels import _BUILTIN_CHANNEL_ADJACENCIES, _BuiltinChannelAdjacency, _ch_neighbor_adjacency, _compute_ch_adjacency
  from mne.datasets import testing
  from mne.io import RawArray, read_info, read_raw_bti, read_raw_ctf, read_raw_eeglab, read_raw_fif, read_raw_kit
  from mne.parallel import parallel_func
  from mne.utils import requires_good_network
label_desc: Use image node_id 13 for calling a global function with example usage: test_drop_channels() without return types