code: function drawGridLines() {
              svg.select('.grid-lines-group')
                  .selectAll('line')
                  .remove();
  
              if (grid === 'horizontal' || grid === 'full') {
                  drawHorizontalGridLines();
              }
  
              if (grid === 'vertical' || grid === 'full') {
                  drawVerticalGridLines();
              }
  
              drawHorizontalExtendedLine();
          }
docs: Draws grid lines on the background of the chart
  @return {void}
  @private