How to use the ccxt.bittrex function in ccxt

async function fetchBalances(keys) {
  portfolio = {};
  if (keys.cex) {
    try {
      cex = new ccxt.cex(keys.cex);
      const cexWallet = await fetch(cex);
    } catch (e) {
      console.log('Failed to fetch Cex', e);
    }
  }

  if (keys.bittrex) {
    try {
      bittrex = new ccxt.bittrex(keys.bittrex);
      const bittrexWallet = await fetch(bittrex);
    } catch (e) {
      console.log('Failed to fetch Bittrex', e);
    }
  }

  if (keys.binance) {
    try {
      binance = new ccxt.binance(keys.binance);
      const binanceWallet = await fetch(binance);
    } catch (e) {
      console.log('Failed fetch Binance', e);
    }
  }

  portfolio.total = calculateTotal();

constructor(auth: ExchangeAuthConfig, logger: Logger) {
        const options = { apiKey: auth.key, secret: auth.secret };
        const ccxtInstance = new bittrex(options);
        super('Bittrex', options, ccxtInstance, logger);
    }
}