code: def test_cell_picking_interactive():
      n_cells = []
  
      def callback(picked_cells):
          n_cells.append(picked_cells.n_cells)
  
      pl = pv.Plotter()
      pl.add_mesh(pv.Sphere())
      pl.enable_cell_picking(callback=callback)
      pl.show(auto_close=False, interactive=False)
  
      width, height = pl.window_size
  
      # simulate "r" keypress
      pl.iren._simulate_keypress("r")
      pl.iren._mouse_left_button_press(width // 2, height // 2)
      pl.iren._mouse_left_button_release(width, height)
  
      assert n_cells[0]
      assert pl.picked_cell
  
imports: import os
  import numpy
  import pytest
  import vtk
  import pyvista
  from pyvista.plotting.errors import PyVistaPickingError
label_desc: Use image node_id 7 for calling a global function with example usage: test_cell_picking_interactive() without return types