code: def test_page_clean_contents():
      """Assert that page contents cleaning actually is invoked."""
      doc = fitz.open()
      page = doc.new_page()
  
      # draw two rectangles - will lead to two /Contents objects
      page.draw_rect((10, 10, 20, 20))
      page.draw_rect((20, 20, 30, 30))
      assert len(page.get_contents()) == 2
      assert page.read_contents().startswith(b"q") == False
  
      # clean / consolidate into one /Contents object
      page.clean_contents()
      assert len(page.get_contents()) == 1
      assert page.read_contents().startswith(b"q") == True
  
imports: import io
  import os
  import fitz
  import pickle
label_desc: Use image node_id 9 for calling a global function with example usage: test_page_clean_contents() without return types