docs: def _compress(compress):
      '''
      Resolve compression flags
      '''
      if compress in ('bz2', 'bzip2', 'j'):
          compression = 'j'
          ext = 'bz2'
      elif compress in ('gz', 'gzip', 'z'):
          compression = 'z'
          ext = 'gz'
      elif compress in ('xz', 'a', 'J'):
          compression = 'J'
          ext = 'xz'
  
      return compression, ext