code: function exportChart(d3svg, filename, title) {
          if (isIE) {
              console.error(IE_ERROR_MSG);
  
              return false;
          }
  
          let img = createImage(convertSvgToHtml.call(this, d3svg, title));
  
          img.onload = handleImageLoad.bind(
                  img,
                  createCanvas(this.width(), this.height()),
                  filename
              );
      }
docs: Main function to be used as a method by chart instances to export charts to png
  @param  {array} svgs         (or an svg element) pass in both chart & legend as array or just chart as svg or in array
  @param  {string} filename    [download to be called <filename>.png]
  @param  {string} title       Title for the image