docs: def send(self, content_type='HTML'):
          """ Takes the recipients, body, and attachments of the Message and sends.
  
          Args:
              content_type: Can either be 'HTML' or 'Text', defaults to HTML.
  
          """
  
          payload = self.api_representation(content_type)
  
          endpoint = 'https://outlook.office.com/api/v1.0/me/sendmail'
          self._make_api_call('post', endpoint=endpoint, data=json.dumps(payload))