Returns the values of the given axis from all the datasets within
        this chart.
        
        :param      axis | <str>
        
        :return     [<variant>, ..]

def values(self, axis):
        """
        Returns the values of the given axis from all the datasets within
        this chart.
        
        :param      axis | <str>
        
        :return     [<variant>, ..]
        """
        output = []
        for dataset in self.datasets():
            output += dataset.values(axis)
        
        return output