'Calculate the Interactive Brokers commission for
a transaction. This is based on the US Fixed pricing,
the details of which can be found here:
https://www.interactivebrokers.co.uk/en/index.php?f=1590&p=stocks1'

def calculate_ib_commission(self, quantity, fill_price):

    commission = min(((0.5 * fill_price) * quantity), max(1.0, (0.005 * quantity)))
    return PriceParser.parse(commission)
