How to use the fabric-network.X509WalletMixin function in fabric-network

function init(config_path, root_path) {
    const config = CaliperUtils.parseYaml(config_path);
    networkRoot = root_path;
    ORGS = config.fabric.network;
    isLegacy = (config.info.Version.startsWith('1.0') || config.info.Version.startsWith('1.1'));
    if(!isLegacy){
        Gateway = require('fabric-network').Gateway;
        InMemoryWallet = require('fabric-network').InMemoryWallet;
        X509WalletMixin = require('fabric-network').X509WalletMixin;
    }
}

async _addToWallet(org, certificate, key, name) {
        const walletId = FabricNetworkAPI.X509WalletMixin.createIdentity(this.networkUtil.getMspIdOfOrganization(org), certificate, key);
        await this.wallet.import(name, walletId);
        logger.info(`Identity ${name} created and imported to wallet`);
    }