def create_card(self, title=None, subtitle=None, content=None, card_type="Simple"):
        """
        card_obj = JSON card object to substitute the 'card' field in the raw_response
        format:
        {
          "type": "Simple", #COMPULSORY
          "title": "string", #OPTIONAL
          "subtitle": "string", #OPTIONAL
          "content": "string" #OPTIONAL
        }
        """
        card = {"type": card_type}
        if title: card["title"] = title
        if subtitle: card["subtitle"] = subtitle
        if content: card["content"] = content
        return card