'Upon receipt of a FillEvent, the PortfolioHandler converts
the event into a transaction that gets stored in the Portfolio
object. This ensures that the broker and the local portfolio
are "in sync".
In addition, for backtesting purposes, the portfolio value can
be reasonably estimated in a realistic manner, simply by
modifying how the ExecutionHandler object handles slippage,
transaction costs, liquidity and market impact.'

def _convert_fill_to_portfolio_update(self, fill_event):

    action = fill_event.action
    ticker = fill_event.ticker
    quantity = fill_event.quantity
    price = fill_event.price
    commission = fill_event.commission
    self.portfolio.transact_position(action, ticker, quantity, price, commission)
