public function append($name, $content)
    {
        if (!is_string($name)) {
            throw new \Exception('Invalid body segment key ("' . gettype($name) . '")');
        }

        if (isset($this->_body[$name])) {
            unset($this->_body[$name]);
        }

        $this->_body[$name] = (string) $content;
        return $this;
    }