code: def genome_for_reference_name(
          reference_name,
          allow_older_downloaded_release=True):
      
      reference_name = normalize_reference_name(reference_name)
      species = find_species_by_reference(reference_name)
      (min_ensembl_release, max_ensembl_release) = \
          species.reference_assemblies[reference_name]
      if allow_older_downloaded_release:
          # go through candidate releases in descending order
          for release in reversed(range(min_ensembl_release, max_ensembl_release + 1)):
              # check if release has been locally downloaded
              candidate = EnsemblRelease.cached(release=release, species=species)
              if candidate.required_local_files_exist():
                  return candidate
          # see if any of the releases between [max, min] are already locally
          # available
      return EnsemblRelease.cached(release=max_ensembl_release, species=species)
docs: Given a genome reference name, such as "GRCh38", returns the
      corresponding Ensembl Release object.
  
      If `allow_older_downloaded_release` is True, and some older releases have
      been downloaded, then return the most recent locally available release.
  
  
      Otherwise, return the newest release of Ensembl (even if its data hasn't
      already been downloaded).