code: def test_xdawn():
      """Test init of xdawn."""
      # Init xdawn with good parameters
      Xdawn(
          n_components=2,
          correct_overlap="auto",
          signal_cov=None,
          reg=None,
      )
      # Init xdawn with bad parameters
      pytest.raises(ValueError, Xdawn, correct_overlap="foo")
  
file_path: mne-python/mne/preprocessing/tests/test_xdawn.py
imports: from pathlib import Path
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_almost_equal, assert_array_equal
  from scipy import stats
  from mne import Epochs, EpochsArray, compute_raw_covariance, create_info, pick_types, read_events
  from mne.decoding import Vectorizer
  from mne.fixes import _safe_svd
  from mne.io import read_raw_fif
  from mne.preprocessing.xdawn import Xdawn, _XdawnTransformer
label_desc: Use image node_id 2 for calling a global function with example usage: test_xdawn() without return types