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
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.