Build :class:`~mwtab.mwtab.MWTabFile` instance.

        :param mwtab_str: String in `mwtab` format.
        :type mwtab_str: :py:class:`str` or :py:class:`bytes`
        :return: instance of :class:`~mwtab.mwtab.MWTabFile`.
        :rtype: :class:`~mwtab.mwtab.MWTabFile`

def _build_mwtabfile(self, mwtab_str):
        """Build :class:`~mwtab.mwtab.MWTabFile` instance.

        :param mwtab_str: String in `mwtab` format.
        :type mwtab_str: :py:class:`str` or :py:class:`bytes`
        :return: instance of :class:`~mwtab.mwtab.MWTabFile`.
        :rtype: :class:`~mwtab.mwtab.MWTabFile`
        """
        mwtab_file = self
        lexer = tokenizer(mwtab_str)
        token = next(lexer)

        while token.key != "!#ENDFILE":
            if token.key.startswith("#"):
                name = token.key[1:]
                section = self._build_block(lexer)
                if section:
                    mwtab_file[name] = section
            token = next(lexer)
        return mwtab_file