Convert file to bz2-compressed file.
        :return: None
        :rtype: :py:obj:`None`

def _to_bz2file(self, file_generator):
        """Convert file to bz2-compressed file.
        :return: None
        :rtype: :py:obj:`None`
        """
        with bz2.BZ2File(file_generator.to_path, mode="wb") as outfile:
            for f in file_generator:
                outfile.write(f.writestr(file_generator.to_format).encode())