code: function( element ) {
          var i;
  
          element = $.getElement( element );
          i = getOverlayIndex( this.currentOverlays, element );
  
          if (i >= 0) {
              return this.currentOverlays[i];
          } else {
              return null;
          }
      }
docs: Finds an overlay identified by the reference element or element id
  and returns it as an object, return null if not found.
  @method
  @param {Element|String} element - A reference to the element or an
  element id which represents the overlay content.
  @return {OpenSeadragon.Overlay} the matching overlay or null if none found.