def _desy_bookkeeping(self, key, value):
    """Populate the ``_desy_bookkeeping`` key."""
    return {
        'date': normalize_date(value.get('d')),
        'expert': force_single_element(value.get('a')),
        'status': value.get('s'),
    }
Populate the ``_desy_bookkeeping`` key.