code: def read_component_sitemap(
              self, sitemapindex_uri, sitemap_uri, sitemap, sitemapindex_is_file):
          
          if (sitemapindex_is_file):
              if (not self.is_file_uri(sitemap_uri)):
                  # Attempt to map URI to local file
                  remote_uri = sitemap_uri
                  sitemap_uri = self.mapper.src_to_dst(remote_uri)
                  self.logger.info(
                      "Mapped %s to local file %s" %
                      (remote_uri, sitemap_uri))
              else:
                  # The individual sitemaps should be at a URL (scheme/server/path)
                  # that the sitemapindex URL can speak authoritatively about
                  if (self.check_url_authority and
                          not UrlAuthority(sitemapindex_uri).has_authority_over(sitemap_uri)):
                      raise ListBaseIndexError(
                          "The sitemapindex (%s) refers to sitemap at a location it does not have authority over (%s)" %
                          (sitemapindex_uri, sitemap_uri))
          try:
              fh = URLopener().open(sitemap_uri)
              self.num_files += 1
          except IOError as e:
              raise ListBaseIndexError(
                  "Failed to load sitemap from %s listed in sitemap index %s (%s)" %
                  (sitemap_uri, sitemapindex_uri, str(e)))
          # Get the Content-Length if we can (works fine for local files)
          try:
              self.content_length = int(fh.info()['Content-Length'])
              self.bytes_read += self.content_length
          except KeyError:
              # If we don't get a length then c'est la vie
              pass
          self.logger.info(
              "Reading sitemap from %s (%d bytes)" %
              (sitemap_uri, self.content_length))
          component = sitemap.parse_xml(fh=fh, sitemapindex=False)
          # Copy resources into self, check any metadata
          for r in component:
              self.resources.add(r)
docs: Read a component sitemap of a Resource List with index.
  
          Each component must be a sitemap with the