The FeeModule contract proxies the Exchange's matchOrders function and refunds orders' fees if they are charged more than the operator's intent.
The contract exposes a single main entry point:
function matchOrders(
Order memory takerOrder,
Order[] memory makerOrders,
uint256 takerFillAmount,
uint256[] memory makerFillAmounts,
uint256 takerFeeAmount,
uint256[] memory makerFeeAmounts
) external;