def METHOD_NAME(self, idx, image, alpha=None, name=None):
    if alpha is None:
        alpha = 1.0
    if name is None:
        name = "layer%d" % (self.cnt)
        self.cnt += 1
    bnch = Bunch.Bunch(image=image, alpha=alpha, name=name)
    self._layer.insert(idx, bnch)