从Lambda返回给Lex的带有附件的响应卡不包含附件

我使用Python编写的AWS Lambda函数返回带有附件的响应卡(根据 https://docs.aws.amazon.com/lex/latest/dg/lambda-input-response-format.html#using-lambda-response-format 和 Hyperlink in response card button in Amazon Lex

def close_response_card(session_attributes, fulfillment_state, message):
    return {
    'sessionAttributes': session_attributes,
    "dialogAction": {
        "type": "Close",
        "fulfillmentState": fulfillment_state,
        'message': message,
        "responseCard": {
            "version": 1,
            "contentType": "application/vnd.amazonaws.card.generic",
            'genericAttachments': [
                {
                    'title': 'Here is a list of hospitals',
                    'subTitle': 'Below is a map',
                    'attachmentLinkUrl': 'https://www.google.com/maps/search/?api=1&query=nearby+hospitals',
                    'imageUrl': 'https://images.sftcdn.net/images/t_optimized,f_auto/p/95612986-96d5-11e6-af7c-00163ec9f5fa/3771854867/google-maps-screenshot.png'
            }
        ]
     }
  }
    }

我想创建一张卡片,让用户在点击卡片后下载一些文件。