Override fields on ``self.account``.

def override_account_fields(self,
                                settled_cash=not_overridden,
                                accrued_interest=not_overridden,
                                buying_power=not_overridden,
                                equity_with_loan=not_overridden,
                                total_positions_value=not_overridden,
                                total_positions_exposure=not_overridden,
                                regt_equity=not_overridden,
                                regt_margin=not_overridden,
                                initial_margin_requirement=not_overridden,
                                maintenance_margin_requirement=not_overridden,
                                available_funds=not_overridden,
                                excess_liquidity=not_overridden,
                                cushion=not_overridden,
                                day_trades_remaining=not_overridden,
                                leverage=not_overridden,
                                net_leverage=not_overridden,
                                net_liquidation=not_overridden):
        """Override fields on ``self.account``.
        """
        # mark that the portfolio is dirty to override the fields again
        self._dirty_account = True
        self._account_overrides = kwargs = {
            k: v for k, v in locals().items() if v is not not_overridden
        }
        del kwargs['self']