code: def create_card(self, title=None, subtitle=None, content=None, card_type="Simple"):
          
          card = {"type": card_type}
          if title: card["title"] = title
          if subtitle: card["subtitle"] = subtitle
          if content: card["content"] = content
          return card
docs: 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
          }