protected function map() {
		/** @var string|null $sample */
		$sample = $this->f('dfSample');
		/** @var string[] $values */
		$values = [self::_DEFAULT, self::$UCFIRST, self::$UCWORDS, self::$UPPERCASE, self::$LOWERCASE];
		/** @var string[] $labels */
		$labels = [
			'As Is'
			, 'Uppercase first letter'
			, 'Uppercase Each Word\'s First Letter'
			,'UPPERCASE'
			,'lowercase'
		];
		return array_combine(
			$values
			,!$sample
			? $labels
			: array_map(function($value, $label) use($sample) {
				return sprintf('%s (%s)', self::apply($sample, $value), $label);
			}, $values, $labels)
			//: df_map([__CLASS__, 'apply'], $keys, [], $sample)
		);
	}