<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def mimes(self):
 """ Returns extended MimeTypes. """

        _mimes = MimeTypes(strict=False)
        _mimes.suffix_map.update({'.tbz2': '.tar.bz2'})
        _mimes.encodings_map.update({'.bz2': 'bzip2'})

        if cfg['CFG_BIBDOCFILE_ADDITIONAL_KNOWN_MIMETYPES']:
            for key, value in iteritems(
                    cfg['CFG_BIBDOCFILE_ADDITIONAL_KNOWN_MIMETYPES']):
                _mimes.add_type(key, value)
                del key, value

        return _mimes