private function prepareContent($content)
    {
        $this->content = $content;

        if (!($this->content instanceof StreamInterface)) {
            $this->content = Stream::factory($this->content);
        } elseif ($this->content instanceof MultipartBody) {
            if (!$this->hasHeader('Content-Disposition')) {
                $disposition = 'form-data; name="' . $this->name .'"';
                $this->headers['Content-Disposition'] = $disposition;
            }

            if (!$this->hasHeader('Content-Type')) {
                $this->headers['Content-Type'] = sprintf(
                    "multipart/form-data; boundary=%s",
                    $this->content->getBoundary()
                );
            }
        }
    }