code: def test_canvas_change():
      fig = plt.figure()
      # Replaces fig.canvas
      canvas = FigureCanvasBase(fig)
      # Should still work.
      plt.close(fig)
      assert not plt.fignum_exists(fig.number)
  
imports: import re
  from matplotlib import path, transforms
  from matplotlib.backend_bases import FigureCanvasBase, KeyEvent, LocationEvent, MouseButton, MouseEvent, NavigationToolbar2, RendererBase
  from matplotlib.backend_tools import RubberbandBase
  from matplotlib.figure import Figure
  from matplotlib.testing._markers import needs_pgf_xelatex
  import matplotlib.pyplot
  import numpy
  import pytest
label_desc: Use image node_id 4 for calling a global function with example usage: test_canvas_change() without return types