'Return (lowers,uppers) for filled contours.'

def _get_lowers_and_uppers(self):

    lowers = self._levels[:(-1)]
    if (self.zmin == lowers[0]):
        lowers = lowers.copy()
        if self.logscale:
            lowers[0] = (0.99 * self.zmin)
        else:
            lowers[0] -= 1
    uppers = self._levels[1:]
    return (lowers, uppers)
