code: function(tableRow, placeHolder, /* optional extra decoration */ decorateImageClass, /* optional sprite class for extra decoration */ spriteClass){
  			var expandImage = document.createElement("span"); //$NON-NLS-0$
  			expandImage.id = this.expandCollapseImageId(tableRow.id);
  			placeHolder.appendChild(expandImage);
  			expandImage.classList.add(this._twistieSpriteClass);
  			expandImage.classList.add(this._collapseImageClass);
  			tableRow.setAttribute("aria-expanded", false);
  			if (decorateImageClass) {
  				var decorateImage = document.createElement("span"); //$NON-NLS-0$
  				placeHolder.appendChild(decorateImage);
  				decorateImage.classList.add(spriteClass || "imageSprite"); //$NON-NLS-0$
  				decorateImage.classList.add(decorateImageClass);
  			}
  			return expandImage;
  		}
docs: Appends the image node with expand/collapse behavior
  @param {Element} tableRow
  @param {Element} placeHolder
  @param {String} decorateImageClass
  @param {String} spriteClass
  @returns {Element} The image node