code: def collection_props(event):
      
      ind = event.ind[0]
      arr = event.artist.get_array()
      # If a constant color/c/z was specified, don't return it
      if arr is None or len(arr) == 1:
          z = None
      else:
          z = arr[ind]
      return dict(z=z, c=z)
docs: Get information for a pick event on an artist collection (e.g.
      LineCollection, PathCollection, PatchCollection, etc).  This will