Sets the drag data for this chart item to the inputed data.
        
        :param      data | <QMimeData> || None

def setDragData(self, data, x=None, y=None):
        """
        Sets the drag data for this chart item to the inputed data.
        
        :param      data | <QMimeData> || None
        """
        self._dragData[(x, y)] = data