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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 _dates(self, key, value):
 """Don't populate any key through the return value. On the other hand, populates the ``date_proposed``, ``date_approved``, ``date_started``, ``date_cancelled``, and the ``date_completed`` keys through side effects. """

    if value.get('q'):
        self['date_proposed'] = normalize_date(value['q'])
    if value.get('r'):
        self['date_approved'] = normalize_date(value['r'])
    if value.get('s'):
        self['date_started'] = normalize_date(value['s'])
    if value.get('c'):
        self['date_cancelled'] = normalize_date(value['c'])
    if value.get('t'):
        self['date_completed'] = normalize_date(value['t'])

    raise IgnoreKey