code: def test_convergence_plot():
      def f(x, y):
          return x**2 + y**2
  
      assert f(2, 2) == 8
  
      x = y = np.linspace(-10, 10, 10)
  
      x, y = np.meshgrid(x, y)
  
      z = f(x, y)
  
      points = np.asarray([x, y, z])
  
      surface.plot(points, colorbar=False)
  
      surface.plot(points, colorbar=True)
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_convergence_plot() and returns: unknown