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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 _is_valid_date(obj, accept_none=True):
 """ Check if an object is an instance of, or a subclass deriving from, a ``date``. However, it does not consider ``datetime`` or subclasses thereof as valid dates. :param obj: Object to test as date. :param accept_none: If True None is considered as a valid date object. """


    if accept_none and obj is None:
        return True
    return isinstance(obj, date) and not isinstance(obj, datetime)