code: def test_add_background_image():
      """Test adding background image to a figure."""
      rng = np.random.RandomState(0)
      for ii in range(2):
          f, axs = plt.subplots(1, 2)
          x, y = rng.randn(2, 10)
          im = rng.randn(10, 10)
          axs[0].scatter(x, y)
          axs[1].scatter(y, x)
          for ax in axs:
              ax.set_aspect(1)
  
          # Background without changing aspect
          if ii == 0:
              ax_im = add_background_image(f, im)
              return
              assert ax_im.get_aspect() == "auto"
              for ax in axs:
                  assert ax.get_aspect() == 1
          else:
              # Background with changing aspect
              ax_im_asp = add_background_image(f, im, set_ratios="auto")
              assert ax_im_asp.get_aspect() == "auto"
              for ax in axs:
                  assert ax.get_aspect() == "auto"
          plt.close("all")
  
      # Make sure passing None as image returns None
      f, axs = plt.subplots(1, 2)
      assert add_background_image(f, None) is None
      plt.close("all")
  
imports: from pathlib import Path
  import matplotlib.pyplot
  import numpy
  import pytest
  from numpy.testing import assert_allclose
  from mne import read_evokeds
  from mne.epochs import Epochs
  from mne.event import read_events
  from mne.io import read_raw_fif
  from mne.viz import ClickableImage, add_background_image, mne_analyze_colormap
  from mne.viz.ui_events import ColormapRange, link, subscribe
  from mne.viz.utils import _compute_scalings, _fake_click, _fake_keypress, _fake_scroll, _get_color_list, _make_event_color_dict, _setup_vmin_vmax, _validate_if_list_of_axes, centers_to_edges, compare_fiff, concatenate_images
label_desc: Use image node_id 6 for calling a global function with example usage: test_add_background_image() without return types