code: def test_get_3d_backend(renderer):
      """Test get_3d_backend function call for side-effects."""
      # Test twice to ensure the first call had no side-effect
      orig_backend = renderer.MNE_3D_BACKEND
      assert renderer.get_3d_backend() == orig_backend
      assert renderer.get_3d_backend() == orig_backend
  
file_path: mne-python/mne/viz/backends/tests/test_renderer.py
imports: import os
  import platform
  import sys
  import numpy
  import pytest
  from mne.utils import run_subprocess
  from mne.viz import Figure3D, get_3d_backend, set_3d_backend
  from mne.viz.backends._utils import ALLOWED_QUIVER_MODES
  from mne.viz.backends.renderer import _get_renderer
  from mne.viz.backends.tests._utils import skips_if_not_pyvistaqt
label_desc: Use image node_id 4 for calling a global function with example usage: test_get_3d_backend(renderer) without return types