function IdMap(address bidder) external view returns (uint8 id);

    /**
     * @dev Packed Bid details into a uint256 for submission.
     *
     * @param bidPrice Price per item.
     * @param itemsToBuy Items to buy in the auction.
     * @param bidderId Id for bidder
     * @return packedBid for auction submission
     */
    function packBid(uint256 bidPrice, uint256 itemsToBuy, uint256 bidderId)
        external
        pure
        returns (uint256 packedBid);

    /**
     * @dev Retrieve information about a bidder after auction settlement.
     *
     * @param slot The slot identifier of the auction.
     * @param bidder The address of the bidder for whom information is requested.
     * @return itemsBought The number of items bought by the bidder in the specified auction.
     * @return amountOwed The amount owed by the bidder for the items bought in the specified auction.
     *
     * Requirements:
     * - The auction must have been settled.
     * - The provided `bidder` address must be valid and have participated in the auction.
     *
     */
    function getBidderInfo(uint256 slot, address bidder)
        external
        view
        returns (uint120 itemsBought, uint128 amountOwed);