public function addLog($key, $message)
    {
        if (!is_string($message)) {
            throw new \InvalidArgumentException(sprintf(
                '[%s]: "message" must be type of string, %s given.',
                __METHOD__,
                gettype($message)
            ));
        }

        if (!isset($this->logs[$key])) {
            $this->logs[$key] = [];
        }

        $this->logs[$key][] = $message;

        return $this;
    }