docs: def _build_package_finder(self, options, index_urls):
          """
          Create a package finder appropriate to this install command.
          This method is meant to be overridden by subclasses, not
          called directly.
          """
          return PackageFinder(find_links=options.find_links,
                               index_urls=index_urls,
                               use_mirrors=options.use_mirrors,
                               mirrors=options.mirrors)