How to use the web3-provider-engine/subproviders/fixture.js function in web3-provider-engine

if(!privateKey) {
        privateKey = Wallet.generate().getPrivateKeyString().slice(2);
        if(localStorage) {
        localStorage.setItem("localPrivateKey", privateKey)}
      }
      // This uses web3-provider-engine and ethereumjs-wallet to construct a
      // wallet in-browser, without needing Metamask, Toshi, etc.
      //
      // Note that the current version of ethereumjs-wallet on npm has a bug,
      // but the latest on Github works just fine.
      var wallet = Wallet.fromPrivateKey(new Buffer(privateKey, "hex"));
      this.engine = new ProviderEngine();
      this.web3 = new Web3(this.engine);
      console.log(this.web3)
      // static results
      this.engine.addProvider(new FixtureSubprovider({
        web3_clientVersion: 'ProviderEngine/v0.0.0/javascript',
        net_listening: true,
        eth_hashrate: '0x00',
        eth_mining: false,
        eth_syncing: true,
      }))

      // filters
      this.engine.addProvider(new FilterSubprovider())

      // id mgmt
      this.engine.addProvider(new WalletSubprovider(wallet, {}))

      this.engine.addProvider(new Web3Subprovider(new Web3.providers.HttpProvider(rpcURL)));

      this.engine.on('block', function(block) {

function metamaskProvider(opts){

  var engine = new ProviderEngine()

  // nonce tracker
  engine.addProvider(new NonceTrackerSubprovider())

  // cache layer
  engine.addProvider(new CacheSubprovider())

  // static results
  engine.addProvider(new FixtureSubprovider({
    web3_clientVersion: 'MetaMask-ProviderEngine/v0.0.0/javascript',
    net_listening: true,
    eth_hashrate: '0x0',
    eth_mining: false,
    eth_syncing: true,
  }))

  // filters
  engine.addProvider(new FilterSubprovider())

  // vm
  engine.addProvider(new VmSubprovider())

  // id mgmt
  engine.addProvider(new HookedWalletSubprovider({
    getAccounts: opts.getAccounts,

this.web3 = new Web3(options.currentProvider);
    } else if (window && window.web3) {
      this.web3 = new Web3(window.web3.currentProvider);
    } else {
      var privateKey = options.privateKey || localStorage.getItem("localPrivateKey");
      if (!privateKey) {
        privateKey = Wallet.generate().getPrivateKeyString().slice(2);
        if (localStorage) {
          localStorage.setItem("localPrivateKey", privateKey);
        }
      }
      var wallet = Wallet.fromPrivateKey(new Buffer(privateKey, "hex"));
      this.engine = new ProviderEngine();
      this.web3 = new Web3(this.engine);
      // static results
      this.engine.addProvider(new FixtureSubprovider({
        web3_clientVersion: 'ProviderEngine/v0.0.0/javascript',
        net_listening: true,
        eth_hashrate: '0x00',
        eth_mining: false,
        eth_syncing: true
      }));

      // filters
      this.engine.addProvider(new FilterSubprovider());

      // id mgmt
      this.engine.addProvider(new WalletSubprovider(wallet, {}));

      this.engine.addProvider(new Web3Subprovider(new Web3.providers.HttpProvider(rpcURL)));

      this.engine.on('block', function (block) {

function Provider (rpcUrl, secretSeed) {
  var engine = new ProviderEngine();
  var web3 = new Web3(engine);
  
  engine.addProvider(new FixtureSubprovider({
    web3_clientVersion: 'ProviderEngine/v0.0.0/javascript',
    net_listening: true,
    eth_hashrate: '0x00',
    eth_mining: false,
    eth_syncing: true,
  }));

  // cache layer
  engine.addProvider(new CacheSubprovider());

  // filters 
  engine.addProvider(new FilterSubprovider())

  // pending nonce
  engine.addProvider(new NonceSubprovider());