code: function drawAxisLabels() {
              if (yAxisLabel) {
                  if (yAxisLabelEl) {
                      yAxisLabelEl.remove();
                  }
                  yAxisLabelEl = svg.select('.y-axis-label')
                    .append('text')
                      .classed('y-axis-label-text', true)
                      .attr('x', -chartHeight / 2)
                      .attr('y', yAxisLabelOffset)
                      .attr('text-anchor', 'middle')
                      .attr('transform', 'rotate(270 0 0)')
                      .text(yAxisLabel);
              }
  
              if (xAxisLabel) {
                  if (xAxisLabelEl) {
                      xAxisLabelEl.remove();
                  }
                  xAxisLabelEl = svg.select('.x-axis-label')
                    .append('text')
                      .attr('y', xAxisLabelOffset)
                      .attr('text-anchor', 'middle')
                      .classed('x-axis-label-text', true)
                      .attr('x', chartWidth / 2)
                      .text(xAxisLabel);
              }
          }
docs: Draws the x and y axis custom labels respective groups
  @private