Show the `ImageSegment` on `ax`.

def show(self, ax:plt.Axes=None, figsize:tuple=(3,3), title:Optional[str]=None, hide_axis:bool=True,
        cmap:str='tab20', alpha:float=0.5, **kwargs):
        "Show the `ImageSegment` on `ax`."
        ax = show_image(self, ax=ax, hide_axis=hide_axis, cmap=cmap, figsize=figsize,
                        interpolation='nearest', alpha=alpha, vmin=0)
        if title: ax.set_title(title)