Fail if the given order would cause the magnitude of our position to be
        greater in shares than self.max_shares or greater in dollar value than
        self.max_notional.

def validate(self,
                 asset,
                 amount,
                 portfolio,
                 algo_datetime,
                 algo_current_data):
        """
        Fail if the given order would cause the magnitude of our position to be
        greater in shares than self.max_shares or greater in dollar value than
        self.max_notional.
        """

        if self.asset is not None and self.asset != asset:
            return

        current_share_count = portfolio.positions[asset].amount
        shares_post_order = current_share_count + amount

        too_many_shares = (self.max_shares is not None and
                           abs(shares_post_order) > self.max_shares)
        if too_many_shares:
            self.handle_violation(asset, amount, algo_datetime)

        current_price = algo_current_data.current(asset, "price")
        value_post_order = shares_post_order * current_price

        too_much_value = (self.max_notional is not None and
                          abs(value_post_order) > self.max_notional)

        if too_much_value:
            self.handle_violation(asset, amount, algo_datetime)