PyGUI - class RadioGroup

# class `RadioGroup`

A RadioGroup is used to coordinate the activity of a group of RadioButtons. It ensures that only one of the RadioButtons is on at a time, and provides a `value` property which is equal to the `value` of the currently selected RadioButton. It also provides an `action` property which is invoked when the user changes the selection.

## Properties

`value`
  The value of the currently selected RadioButton. Setting this property updates the states of the RadioButtons accordingly.

> `action`
>   Action to perform when the value changes as a result of the user clicking on a radio button.

## Constructor

`RadioGroup(items)`
  Constructs a RadioGroup containing the given list of RadioButtons.

## Methods

`add(`item, ...`)`
  Adds the specified RadioButtons to this group.

`remove(`item, ...`)`
  Removes the specified RadioButtons from this group.

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