code: function drawHorizontalExtendedLine() {
              baseLine = svg.select('.grid-lines-group')
                  .selectAll('line.extended-x-line')
                  .data([0])
                  .enter()
                    .append('line')
                      .attr('class', 'extended-x-line')
                      .attr('x1', xAxisPadding.left)
                      .attr('x2', chartWidth)
                      .attr('y1', chartHeight)
                      .attr('y2', chartHeight);
          }
docs: Draws a vertical line to extend x-axis till the edges
  @return {void}
  @private