code: def test_vis_image(self):
      ax = vis_image(self.img)
      self.assertTrue(isinstance(ax, matplotlib.axes.Axes))
  
imports: import unittest
  import numpy
  from chainercv.utils import testing
  from chainercv.visualizations import vis_image
label_desc: Use image node_id 1 for calling the TestVisImage obj's underlying member method code with example usage: obj.test_vis_image() without return types