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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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'),
    }