def lowerbound(self, axis=0):
        """
        Get the lower bound of the binning along an axis
        """
        if not 0 <= axis < self.GetDimension():
            raise ValueError(
                "axis must be a non-negative integer less than "
                "the dimensionality of the histogram")
        if axis == 0:
            return self.xedges(1)
        if axis == 1:
            return self.yedges(1)
        if axis == 2:
            return self.zedges(1)
        raise TypeError("axis must be an integer")
Get the lower bound of the binning along an axis