code: function drawBrush() {
              chartBrush = svg.select('.brush-group')
                                  .call(brush);
  
              // Update the height of the brushing rectangle
              chartBrush.selectAll('rect')
                  .classed('brush-rect', true)
                  .attr('height', chartHeight);
  
              chartBrush.selectAll('.selection')
                  .attr('fill', `url(#${gradientId})`);
          }
docs: Draws the Brush components on its group
  @return {void}