function addHolding(
    CrossMarginAccount storage account,
    address token,
    uint256 depositAmount
) internal {
    if (!hasHoldingToken(account, token)) {
        // SHOULD SET account.holdsToken here
        account.holdingTokens.push(token);
    }

    account.holdings[token] += depositAmount;
}
function getHoldingAmounts(address trader)
    external
    view
    override
    returns (
        address[] memory holdingTokens,
        uint256[] memory holdingAmounts
    )
{
    CrossMarginAccount storage account = marginAccounts[trader];
    holdingTokens = account.holdingTokens;

    holdingAmounts = new uint256[](account.holdingTokens.length);
    for (uint256 idx = 0; holdingTokens.length > idx; idx++) {
        address tokenAddress = holdingTokens[idx];
        // RETURNS SUM OF THE BALANCE FOR EACH TOKEN ENTRY
        holdingAmounts[idx] = account.holdings[tokenAddress];
    }
}
function crossCloseAccount() external {
    (address[] memory holdingTokens, uint256[] memory holdingAmounts) =
        IMarginTrading(marginTrading()).getHoldingAmounts(msg.sender);

    // requires all debts paid off
    IMarginTrading(marginTrading()).registerLiquidation(msg.sender);

    for (uint256 i; holdingTokens.length > i; i++) {
        Fund(fund()).withdraw(
            holdingTokens[i],
            msg.sender,
            holdingAmounts[i]
        );
    }
}
