docs: function(datasetIndex, name) {
  		var stacks = this._getStacks(datasetIndex);
  		var index = (name !== undefined)
  			? stacks.indexOf(name)
  			: -1; // indexOf returns -1 if element is not present
  
  		return (index === -1)
  			? stacks.length - 1
  			: index;
  	}