code: def test_plot_snr():
      """Test plotting SNR estimate."""
      inv = read_inverse_operator(inv_fname)
      evoked = read_evokeds(evoked_fname, baseline=(None, 0))[0]
      plot_snr_estimate(evoked, inv)
  
imports: from pathlib import Path
  import matplotlib.pyplot
  import numpy
  import pytest
  from numpy.testing import assert_array_equal
  from mne import SourceEstimate, pick_events, read_cov, read_dipole, read_events, read_evokeds, read_source_spaces
  from mne.chpi import compute_chpi_snr
  from mne.datasets import testing
  from mne.filter import create_filter
  from mne.io import read_raw_fif
  from mne.minimum_norm import read_inverse_operator
  from mne.time_frequency import CrossSpectralDensity
  from mne.viz import plot_bem, plot_chpi_snr, plot_csd, plot_events, plot_filter, plot_snr_estimate, plot_source_spectrogram
  from mne.viz.misc import _handle_event_colors
  from mne.viz.utils import _get_color_list
label_desc: Use image node_id 9 for calling a global function with example usage: test_plot_snr() without return types