docs: 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)