Sets the vertical axis for this chart.
        
        :param      axis | <XChartAxis>

def setVerticalAxis(self, axis):
        """
        Sets the vertical axis for this chart.
        
        :param      axis | <XChartAxis>
        """
        self._verticalAxis = axis
        if axis:
            axis.setOrientation(Qt.Vertical)
            self.uiYAxisVIEW.setFixedWidth(axis.minimumLabelWidth() + 15)
        
        self.uiYAxisVIEW.setVisible(axis is not None)