function exit(bytes32 _listingHash) external {
        Listing storage listing = listings[_listingHash];

        require(msg.sender == listing.owner);
        require(isWhitelisted(_listingHash));

        
        require(listing.challengeID == 0 || challenges[listing.challengeID].resolved);

        
        resetListing(_listingHash);
        _ListingWithdrawn(_listingHash);
    }