code: def test_themes(theme):
      try:
          pv.set_plot_theme(theme.name)
          assert pv.global_theme == theme.value()
      finally:
          # always return to testing theme
          pv.set_plot_theme("testing")
  
imports: import os
  import pytest
  import vtk
  import pyvista
  from pyvista import colors
  from pyvista.examples.downloads import download_file
  from pyvista.plotting.themes import DarkTheme, Theme, _set_plot_theme_from_env
  from pyvista.plotting.utilities.gl_checks import uses_egl
label_desc: Use image node_id 27 for calling a global function with example usage: test_themes(theme) without return types