code: function buildAxis() {
              xAxis = d3Axis.axisBottom(xScale)
                  .ticks(xTicks)
                  .tickPadding(tickPadding)
                  .tickFormat(d3Format.format(xAxisFormat));
  
              yAxis = d3Axis.axisLeft(yScale)
                  .ticks(yTicks)
                  .tickPadding(tickPadding)
                  .tickFormat(d3Format.format(yAxisFormat));
          }
docs: Creates the x-axis and y-axis with proper orientations
  @return {void}
  @private