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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _is_nmrstar(string):
 """Test if input string is in NMR-STAR format. :param string: Input string. :type string: :py:class:`str` or :py:class:`bytes` :return: Input string if in NMR-STAR format or False otherwise. :rtype: :py:class:`str` or :py:obj:`False` """

        if (string[0:5] == u"data_" and u"save_" in string) or (string[0:5] == b"data_" and b"save_" in string):
            return string
        return False