Function getDepthCache

deprecated/node-binance-api.js:2587–2590

     * @return {object} - the depth cache object
     */
    const getDepthCache = symbol => {
        if (typeof Binance.depthCache[symbol] === 'undefined') return { bids: {}, asks: {} };
        return Binance.depthCache[symbol];
    };

    /**
     * Calculate Buy/Sell volume from DepthCache