Send request to Postmark API.
        Returns result of :func:`requests.post`.

        :param message: Your Postmark message data.
        :type message: `dict` or :class:`Message`
        :param api_key: Your Postmark API key.
        :type api_key: `str`
        :param test: Make a test request to the Postmark API.
        :param secure: Use the https Postmark API.
        :param \*\*request_args: Passed to :func:`requests.post`
        :rtype: :class:`requests.Response`

def send(self, message=None, api_key=None, secure=None, test=None,
             **request_args):
        '''Send request to Postmark API.
        Returns result of :func:`requests.post`.

        :param message: Your Postmark message data.
        :type message: `dict` or :class:`Message`
        :param api_key: Your Postmark API key.
        :type api_key: `str`
        :param test: Make a test request to the Postmark API.
        :param secure: Use the https Postmark API.
        :param \*\*request_args: Passed to :func:`requests.post`
        :rtype: :class:`requests.Response`
        '''
        headers = self._get_headers(api_key=api_key, test=test,
                                    request_args=request_args)
        data = self._get_request_content(message)
        url = self._get_api_url(secure=secure)
        return self._request(url, data=data, headers=headers, **request_args)