static _extractColumnSurvivalRateStatsFromPixelDatas(normsPixelData) {
        let curSurvivalRate = 1;
        let survivalRates = [];
        for (let col = 0; col < normsPixelData.length; col++) {
            if (normsPixelData[col].length > 0) {
                curSurvivalRate = normsPixelData[col][0];
            }
            survivalRates.push(curSurvivalRate);
        }
        return survivalRates;
    }
@param {!Array.<!Float32Array>} normsPixelData
@returns {!Array.<!number>}
@private