code: def add_basemap(ax, zoom=12):
      
      url = ctx.sources.ST_TONER_LITE
      xmin, xmax, ymin, ymax = ax.axis()
      basemap, extent = ctx.bounds2img(xmin, ymin, xmax, ymax,
                                              zoom=zoom, url=url)
      ax.imshow(basemap, extent=extent, interpolation='bilinear')
      # restore original x/y limits
      ax.axis((xmin, xmax, ymin, ymax))
docs: Adds map to a plot.