code: def test_plotter_actors(sphere, cube):
      pl = pv.Plotter()
      actor_a = pl.add_mesh(sphere)
      actor_b = pl.add_mesh(cube)
      assert len(pl.actors) == 2
      assert actor_a in pl.actors.values()
      assert actor_b in pl.actors.values()
  
imports: import os
  import numpy
  import pytest
  import vtk
  import pyvista
  from pyvista.core.errors import MissingDataError, PyVistaDeprecationWarning
  from pyvista.plotting import _plotting
  from pyvista.plotting.errors import RenderWindowUnavailable
  from pyvista.plotting.utilities.gl_checks import uses_egl
label_desc: Use image node_id 29 for calling a global function with example usage: test_plotter_actors(sphere, cube) without return types