docs: 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