code: function buildScales() {
              const maxValueByDate = isUsingFakeData ? emptyDataConfig.maxY : getMaxValueByDate();
  
              xScale = d3Scale.scaleTime()
                  .domain(d3Array.extent(dataByDate, ({date}) => date))
                  .rangeRound([0, chartWidth]);
  
              yScale = d3Scale.scaleLinear()
                  .domain([0, maxValueByDate])
                  .rangeRound([chartHeight, 0])
                  .nice();
  
              categoryColorMap =  order.reduce((memo, topic, index) => (
                  assign({}, memo, {[topic]: colorSchema[index]})
              ), {});
          }
docs: Creates the x, y and color scales of the chart
  @private