function drawHorizontalExtendedLine() {
            if (baseLine) {
                baseLine.remove();
            }

            baseLine = svg.select('.axis-group')
              .selectAll('line.extended-x-line')
              .data([0])
              .enter()
                .append('line')
                  .attr('class', 'extended-x-line')
                  .attr('x1', 0)
                  .attr('x2', chartWidth);
        }
Draws a vertical line to extend x-axis till the edges
@return {void}
@private