Is there a way to unselect other values if click `none` and clear `none` if other values are clicked?

Panel
1 
import panel as pn
pn.extension()

radio = pn.widgets.CheckButtonGroup(options=["a", "b", "none"])
radio.jscallback(value="""
    var last_index = source.labels.length - 1;
    if (last_index in source.active) {
        source.active = [last_index]
    }
""")

radio

I am unsure how to implement the latter part

2

In python, but it’d be nice if there’s a Javascript equivalent

import panel as pn
pn.extension()

def either_active(event):
    print(event.new)
    if len(event.new) > 1 and "none" in event.old:
        event.obj.value = [value for value in event.new if value != "none"]
    elif "none" in event.new:
        event.obj.value = ["none"]

radio = pn.widgets.CheckButtonGroup(options=["a", "b", "none"])
radio.param.watch(either_active, "value")

radio