docs: def colorline(ax, x, y, z, **kwargs):
      """
      http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb
      http://matplotlib.org/examples/pylab_examples/multicolored_line.html
      Plot a colored line with coordinates x and y
      Optionally specify colors in the array z
      Optionally specify a colormap, a norm function and a line width
      """
  
      # Special case if a single number:
      if not hasattr(z, "__iter__"):  # to check for numerical input -- this is a hack
          z = np.array([z])
  
      z = np.asarray(z)
  
      segments = make_segments(x, y)
      lc = mcoll.LineCollection(segments, array=z, **kwargs)
  
      ax.add_collection(lc)
      if ax.get_autoscale_on():
          ax.autoscale_view()
  
      return lc