new_contents: import matplotlib.pyplot as plt
  import matplotlib.cbook as cbook
  from matplotlib_scalebar.scalebar import ScaleBar, IMPERIAL_LENGTH
  plt.figure()
  image = plt.imread(cbook.get_sample_data('grace_hopper.png'))
  plt.imshow(image)
  scalebar = ScaleBar(0.02, 'ft', IMPERIAL_LENGTH,
                      fixed_value=48.0, fixed_units='in')
  plt.gca().add_artist(scalebar)
  plt.savefig('example3.png')
  
subject: Add example