public function sendHeaders()
    {
        deprecationWarning(
            'Will be removed in 4.0.0'
        );

        $file = $line = null;
        if (headers_sent($file, $line)) {
            Log::warning("Headers already sent in {$file}:{$line}");

            return;
        }

        $codeMessage = $this->_statusCodes[$this->_status];
        $this->_setCookies();
        $this->_sendHeader("{$this->_protocol} {$this->_status} {$codeMessage}");
        $this->_setContentType();

        foreach ($this->headers as $header => $values) {
            foreach ((array)$values as $value) {
                $this->_sendHeader($header, $value);
            }
        }
    }