Adds the given data set to this chart widget.
        
        :param      dataSet | <XChartDataset>

def addDataset(self, dataset):
        """
        Adds the given data set to this chart widget.
        
        :param      dataSet | <XChartDataset>
        """
        self._datasets.append(dataset)
        self._dataChanged = True
        self._addDatasetAction(dataset)