Parse a string to produce a :class:`.Date`.

        Accepted formats:
            'YYYY-MM-DD'

        :param s:
        :return:

def parse(cls, s):
        """ Parse a string to produce a :class:`.Date`.

        Accepted formats:
            'YYYY-MM-DD'

        :param s:
        :return:
        """
        try:
            numbers = map(int, s.split("-"))
        except (ValueError, AttributeError):
            raise ValueError("Date string must be in format YYYY-MM-DD")
        else:
            numbers = list(numbers)
            if len(numbers) == 3:
                return cls(*numbers)
            raise ValueError("Date string must be in format YYYY-MM-DD")