code: function (str) {
  		var chart = this,
  			options = chart.options,
  			loadingDiv = chart.loadingDiv;
  
  		var loadingOptions = options.loading;
  
  		// create the layer at the first call
  		if (!loadingDiv) {
  			chart.loadingDiv = loadingDiv = createElement(DIV, {
  				className: PREFIX + 'loading'
  			}, extend(loadingOptions.style, {
  				zIndex: 10,
  				display: NONE
  			}), chart.container);
  
  			chart.loadingSpan = createElement(
  				'span',
  				null,
  				loadingOptions.labelStyle,
  				loadingDiv
  			);
  
  		}
  
  		// update text
  		chart.loadingSpan.innerHTML = str || options.lang.loading;
  
  		// show it
  		if (!chart.loadingShown) {
  			css(loadingDiv, { 
  				opacity: 0, 
  				display: '',
  				left: chart.plotLeft + PX,
  				top: chart.plotTop + PX,
  				width: chart.plotWidth + PX,
  				height: chart.plotHeight + PX
  			});
  			animate(loadingDiv, {
  				opacity: loadingOptions.style.opacity
  			}, {
  				duration: loadingOptions.showDuration || 0
  			});
  			chart.loadingShown = true;
  		}
  	}
docs: Dim the chart and show a loading text or symbol
  @param {String} str An optional text to show in the loading label instead of the default one