code: def tile(self, z, x, y):
          
          logger.debug(_("Download tile %s") % ((z, x, y),))
          # Render each keyword in URL ({s}, {x}, {y}, {z}, {size} ... )
          size = self.tilesize
          s = self.tiles_subdomains[(x + y) % len(self.tiles_subdomains)];
          try:
              url = self.tiles_url.format(**locals())
          except KeyError as e:
              raise DownloadError(_("Unknown keyword %s in URL") % e)
  
          logger.debug(_("Retrieve tile at %s") % url)
          r = DOWNLOAD_RETRIES
          sleeptime = 1
          while r > 0:
              try:
                  request = requests.get(url, headers=self.headers)
                  if request.status_code == 200:
                      return request.content
                  raise DownloadError(_("Status code : %s, url : %s") % (request.status_code, url))
              except requests.exceptions.ConnectionError as e:
                  logger.debug(_("Download error, retry (%s left). (%s)") % (r, e))
                  r -= 1
                  time.sleep(sleeptime)
                  # progressivly sleep longer to wait for this tile
                  if (sleeptime <= 10) and (r % 2 == 0):
                      sleeptime += 1  # increase wait
          raise DownloadError(_("Cannot download URL %s") % url)
docs: Download the specified tile from `tiles_url`