code: def file_xext(filepath):
      
      ext = os.path.splitext(filepath)[1]
      if ext == '.gz':
          xext = os.path.splitext(os.path.splitext(filepath)[0])[1]
          if xext == '.tar':
              ext = xext + ext
      elif ext == '.tar':
          pass # ext is already .tar
      else:
          ext = ''
      return ext
docs: Get the file extension wrt compression from the filename (is it tar or targz)
      :param str filepath: Path to the file
      :return str ext: Compression extension name