@staticmethod
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
