Radio group governs the set of
radio objects. At each given moment of time only one of the objects in the "on" state and the rest are in the "off" state.
method on_state_change : ?switch:LTerm_widget_callbacks.switch -> ('a option -> unit) -> unit
on_state_change ?switch f calls
f when the state of the group is changed.
The state of the group. Contains
Some id with the id of "on" object in the group or None if no objects were added to the group yet.
method register_object : 'a radio -> unit
Adds radio object to the group