def test_light_source_masked_shading():
        """Array comparison test for a surface with a masked portion. Ensures that
        we don't wind up with "fringes" of odd colors around masked regions."""
        y, x = np.mgrid[-1.2:1.2:8j, -1.2:1.2:8j]
        z = 10 * np.cos(x**2 + y**2)
    
        z = np.ma.masked_greater(z, 9.9)
    
        cmap = plt.cm.copper
        ls = mcolors.LightSource(315, 45)
>       rgb = ls.shade(z, cmap)

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-6-96ee2a102cfd> in <module>
      1 cmap = plt.cm.copper
      2 ls = mcolors.LightSource(315, 45)
----> 3 rgb = ls.shade(z, cmap)

~/visualization/matplotlib/lib/matplotlib/colors.py in shade(self, data, cmap, norm, blend_mode, vmin, vmax, vert_exag, dx, dy, fraction, **kwargs)
   1800         rgb1 = self.shade_rgb(rgb0, elevation=data, blend_mode=blend_mode,
   1801                               vert_exag=vert_exag, dx=dx, dy=dy,
-> 1802                               fraction=fraction, **kwargs)
   1803         # Don't overwrite the alpha channel, if present.
   1804         rgb0[..., :3] = rgb1[..., :3]

~/visualization/matplotlib/lib/matplotlib/colors.py in shade_rgb(self, rgb, elevation, fraction, blend_mode, vert_exag, dx, dy, **kwargs)
   1871         # Only apply result where hillshade intensity isn't masked
   1872         if hasattr(intensity, 'mask'):
-> 1873             mask = intensity.mask[..., 0]
   1874             for i in range(3):
   1875                 blend[..., i][mask] = rgb[..., i][mask]

IndexError: invalid index to scalar variable.