How to use the @0x/contracts-asset-proxy.ERC721ProxyContract function in @0x/contracts-asset-proxy

async function testContractConfigsAsync(provider: SupportedProvider): Promise {
    const web3Wrapper = new Web3Wrapper(provider);
    const chainId = await web3Wrapper.getChainIdAsync();
    const addresses = getContractAddressesForChainOrThrow(chainId);
    const configs = getConfigsByChainId(chainId);

    function warnIfMismatch(actual: any, expected: any, message: string): void {
        if (actual !== expected) {
            logUtils.warn(`${message}: actual: ${actual}, expected: ${expected}, chainId: ${chainId}`);
        }
    }

    const exchange = new ExchangeContract(addresses.exchange, provider);
    const exchangeV2 = new ExchangeContract(addresses.exchangeV2, provider);
    const erc20Proxy = new ERC20ProxyContract(addresses.erc20Proxy, provider);
    const erc721Proxy = new ERC721ProxyContract(addresses.erc721Proxy, provider);
    const erc1155Proxy = new ERC1155ProxyContract(addresses.erc1155Proxy, provider);
    const multiAssetProxy = new MultiAssetProxyContract(addresses.multiAssetProxy, provider);
    const erc20BridgeProxy = new ERC20ProxyContract(addresses.erc20BridgeProxy, provider);
    const governor = new ZeroExGovernorContract(addresses.zeroExGovernor, provider);
    const stakingProxy = new StakingProxyContract(addresses.stakingProxy, provider);
    const stakingContract = new StakingContract(addresses.stakingProxy, provider);
    const zrxVault = new ZrxVaultContract(addresses.zrxVault, provider);

    async function verifyExchangeV2ConfigsAsync(): Promise {
        const exchangeOwner = await exchangeV2.owner().callAsync();
        warnIfMismatch(exchangeOwner, governor.address, 'Unexpected ExchangeV2 owner');

        const registeredERC20Proxy = await exchangeV2.getAssetProxy(AssetProxyId.ERC20).callAsync();
        warnIfMismatch(registeredERC20Proxy, erc20Proxy.address, 'Unexpected ERC20Proxy registered in ExchangeV2');

        const registeredERC721Proxy = await exchangeV2.getAssetProxy(AssetProxyId.ERC721).callAsync();