program crashed while calling RequestHandler.get_argument(), tried to avoid auto-decode before value returns, but seems not possible.
the comment of get_argument says:
...The returned values are always unicode.
and after i googled [tornado get_argument unicode], i found this:
see https://github.com/facebook/tornado/issues/407#issuecomment-2971210
so, it's very simple to handle this issue. just override method named "decode_argument".
