Starts a new drag with the inputed data.
        
        :param      dragData | <dict>

def startDrag(self, dragData):
        """
        Starts a new drag with the inputed data.
        
        :param      dragData | <dict>
        """
        # create the mime data
        mimeData = QMimeData()
        for key, value in dragData.items():
            mimeData.setData('application/x-%s' % key, wrapVariant(value))
        
        # create the drag instance
        drag = QDrag(self.scene().chart())
        drag.setMimeData(mimeData)
        drag.exec_()