private function key($method, $type, $alt, $s = null, $throw = true) {return
		$this->$method("{$type}Key", $s, function() use($method, $alt, $s) {return
			$this->$method("{$alt}Key", $s);}
		) ?: ($throw ? df_error("Please set your {$this->titleB()} $type key in the Magento backend.") : null)
	;}