    function withdraw(uint _shares) external {
        settlePendingObligation();
        require(pendingObligation == 0, "IF.withdraw.pending_obligations");
        uint amount = balance() * _shares / totalSupply();
        _burn(msg.sender, _shares);
        vusd.safeTransfer(msg.sender, amount);
        emit FundsWithdrawn(msg.sender, amount, block.timestamp);
    }
    function seizeBadDebt(uint amount) external onlyMarginAccount {
        pendingObligation += amount;
        emit BadDebtAccumulated(amount, block.timestamp);
        settlePendingObligation();
    }
