final protected function map() {
		/** @var array(string => string) $result */ /** @var bool $met */
		$result = df_map_0([], $met = $this->isRequirementMet() ? null : $this->requirement());
		if ($met) {
			try {$result += $this->fetch();}
			catch (\Exception $e) {$result = $this->exception($e);}
		}
		return $result;
	}