Converts map element into a Date or returns None if conversion is not possible.

        :param key: an index of element to get.

        :return: Date value of the element or None if conversion is not supported.

def get_as_nullable_datetime(self, key):
        """
        Converts map element into a Date or returns None if conversion is not possible.

        :param key: an index of element to get.

        :return: Date value of the element or None if conversion is not supported.
        """
        value = self.get(key)
        return DateTimeConverter.to_nullable_datetime(value)