def str2tuple(tt):
    """
  Convert tagged token like 'fly/VB' into a tuple like ('fly', 'VB'). If no '/'
  is found, return (tt, None). If multiple '/' are found, ignore all but the
  last;  e.g., 'on/off/NN' results in ('on/off', 'NN')
  """
    token_tag = tt.rsplit('/', 1)
    assert token_tag[1] is not None
    return token_tag[0], token_tag[1].upper()
