old_contents: from .tarball import TarballArchiver
  from .zipfile import ZipArchiver
  
  
  TARBALL = TarballArchiver.UNCOMPRESSED
  TARBALL_GZ = TarballArchiver.GZ
  TARBALL_BZ2 = TarballArchiver.BZ2
  TARBALL_XZ = TarballArchiver.XZ
  ZIP = 'zip'
  
  FORMATS = (
      (TARBALL, "Tarball (.tar)"),
      (TARBALL_GZ, "gzip-compressed Tarball (.tar.gz)"),
      (TARBALL_BZ2, "bzip2-compressed Tarball (.tar.bz2)"),
      (TARBALL_XZ, "xz-compressed Tarball (.tar.xz)"),
      (ZIP, "ZIP archive (.zip)"),
  )
  
  
  def get_archiver(fmt):
      """
      Return the class corresponding with the provided archival format
      """
      if fmt in (TARBALL, TARBALL_GZ, TARBALL_BZ2, TARBALL_XZ):
          return TarballArchiver
      if fmt == ZIP:
          return ZipArchiver
      raise KeyError("Invalid format '{}' specified".format(fmt))
  
new_contents: from .tarball import TarballArchiver
  from .zipfile import ZipArchiver
  
  
  TARBALL = TarballArchiver.UNCOMPRESSED
  TARBALL_GZ = TarballArchiver.GZ
  TARBALL_BZ2 = TarballArchiver.BZ2
  TARBALL_XZ = TarballArchiver.XZ
  ZIP = 'zip'
  
  FORMATS = (
      TARBALL,
      TARBALL_GZ,
      TARBALL_BZ2,
      TARBALL_XZ,
      ZIP,
  )
  
  FORMATS_DESC = {
      TARBALL: "Tarball (.tar)",
      TARBALL_GZ: "gzip-compressed Tarball (.tar.gz)",
      TARBALL_BZ2: "bzip2-compressed Tarball (.tar.bz2)",
      TARBALL_XZ: "xz-compressed Tarball (.tar.xz)",
      ZIP: "ZIP archive (.zip)",
  }
  
  
  def get_archiver(fmt):
      """
      Return the class corresponding with the provided archival format
      """
      if fmt in (TARBALL, TARBALL_GZ, TARBALL_BZ2, TARBALL_XZ):
          return TarballArchiver
      if fmt == ZIP:
          return ZipArchiver
      raise KeyError("Invalid format '{}' specified".format(fmt))
  
subject: Make FORMATS a tuple and add FORMATS_DESC for textual format descriptions.