code: def select_release(self, highest_allowed_release):
          
          matching_releases = []
          highest_allowed_key = natsort_key(highest_allowed_release)
          for release in self.ordered_releases:
              release_key = natsort_key(release.identifier)
              if release_key <= highest_allowed_key:
                  matching_releases.append(release)
          if not matching_releases:
              msg = "No releases below or equal to %r found in repository!"
              raise NoMatchingReleasesError(msg % highest_allowed_release)
          return matching_releases[-1]
docs: Select the newest release that is not newer than the given release.
  
          :param highest_allowed_release: The identifier of the release that sets
                                          the upper bound for the selection (a
                                          string).
          :returns: The identifier of the selected release (a string).
          :raises: :exc:`~vcs_repo_mgr.exceptions.NoMatchingReleasesError`
                   when no matching releases are found.