'Returns the z-axis numerical bounds where::
lowerBound < upperBound
.. versionadded :: 1.1.0
This function was added, but not tested. Please report any bugs.'

def get_zbound(self):

    (bottom, top) = self.get_zlim()
    if (bottom < top):
        return (bottom, top)
    else:
        return (top, bottom)
