public function selectButtonByIndex($index)
	{
		if ( isset($this[$index]) ) {
			/** @var RadioButton $button */
			$button = $this[$index];
			$button->select();

			return $this;
		}

		throw new RadioGroupException(
			'Cannot locate radio button with index: ' . $index,
			RadioGroupException::TYPE_NOT_FOUND
		);
	}