code: def test_stc_mpl():
      """Test plotting source estimates with matplotlib."""
      pytest.importorskip("nibabel")
      sample_src = read_source_spaces(src_fname)
      vertices = [s["vertno"] for s in sample_src]
      n_time = 5
      n_verts = sum(len(v) for v in vertices)
      stc_data = np.ones(n_verts * n_time)
      stc_data.shape = (n_verts, n_time)
      stc = SourceEstimate(stc_data, vertices, 1, 1, "sample")
      stc.plot(
          subjects_dir=subjects_dir,
          time_unit="s",
          views="ven",
          hemi="rh",
          smoothing_steps=7,
          subject="sample",
          backend="matplotlib",
          spacing="oct1",
          initial_time=0.001,
          colormap="Reds",
      )
      fig = stc.plot(
          subjects_dir=subjects_dir,
          time_unit="ms",
          views="dor",
          hemi="lh",
          smoothing_steps=7,
          subject="sample",
          backend="matplotlib",
          spacing="ico2",
          time_viewer=True,
          colormap="mne",
      )
      time_viewer = fig.time_viewer
      _fake_click(
          time_viewer, time_viewer.axes[0], (0.5, 0.5)
      )  # change t
      _fake_keypress(time_viewer, "ctrl+right")
      _fake_keypress(time_viewer, "left")
      pytest.raises(
          ValueError,
          stc.plot,
          subjects_dir=subjects_dir,
          hemi="both",
          subject="sample",
          backend="matplotlib",
      )
      pytest.raises(
          ValueError,
          stc.plot,
          subjects_dir=subjects_dir,
          time_unit="ss",
          subject="sample",
          backend="matplotlib",
      )
  
imports: from pathlib import Path
  import matplotlib.pyplot
  import numpy
  import pytest
  from matplotlib.colors import Colormap
  from matplotlib.figure import Figure
  from numpy.testing import assert_allclose, assert_array_equal
  from mne import MixedSourceEstimate, SourceEstimate, convert_forward_solution, make_field_map, make_sphere_model, pick_info, pick_types, read_dipole, read_evokeds, read_forward_solution, read_trans, setup_volume_source_space, use_coil_def
  from mne._fiff._digitization import write_dig
  from mne._fiff.constants import FIFF
  from mne.bem import read_bem_solution, read_bem_surfaces
  from mne.datasets import testing
  from mne.defaults import DEFAULTS
  from mne.io import read_info, read_raw_bti, read_raw_ctf, read_raw_kit, read_raw_nirx
  from mne.minimum_norm import apply_inverse
  from mne.source_estimate import _BaseVolSourceEstimate
  from mne.source_space import read_source_spaces
  from mne.transforms import Transform
  from mne.utils import _record_warnings, catch_logging
  from mne.viz import Brain, EvokedField, Figure3D, link_brains, mne_analyze_colormap, plot_alignment, plot_brain_colorbar, plot_head_positions, plot_source_estimates, plot_sparse_source_estimates, snapshot_brain_montage
  from mne.viz._3d import _get_map_ticks, _linearize_map, _process_clim
  from mne.viz.utils import _fake_click, _fake_keypress, _fake_scroll, _get_cmap
label_desc: Use image node_id 13 for calling a global function with example usage: test_stc_mpl() without return types