How to use the node-bitstamp.CURRENCY.LTC_EUR function in node-bitstamp

[CURRENCY.ETH_EUR]: {
        predict: trades => { //before prediction (is called)
            return TRADES_TO_ROW(trades, ETH_EUR_FACTOR);
        },
        main: row => { //before training (is mapped)
           // const trades = row.x.slice(0);
            row.x = TRADES_TO_ROW(row.x, ETH_EUR_FACTOR);
            row.y = TRADES_TO_ROW_OUTPUT(row.y, ETL_FACTOR);
            return row;
        },
        alter: (outputs, tradeForPrediction) => { //after prediction (is called)
            return OUTPUT_TO_TRADE_PRICES(outputs, ETL_FACTOR, tradeForPrediction);
        }
    },

    [CURRENCY.LTC_EUR]: {
        predict: trades => { //before prediction (is called)
            return TRADES_TO_ROW(trades, LTC_EUR_FACTOR);
        },
        main: row => { //before training (is mapped)
           // const trades = row.x.slice(0);
            row.x = TRADES_TO_ROW(row.x, LTC_EUR_FACTOR);
            row.y = TRADES_TO_ROW_OUTPUT(row.y, ETL_FACTOR);
            return row;
        },
        alter: (outputs, tradeForPrediction) => { //after prediction (is called)
            return OUTPUT_TO_TRADE_PRICES(outputs, ETL_FACTOR, tradeForPrediction);
        }
    },
};

const SUM_LAST_ELEMENTS_IN_ARRAY = (a, c = 3) => {

startForLitecoin(){
        return this.start(CURRENCY.LTC_EUR, 3335);
    }