Alexa无法识别有效的json feed

Question

  

错误：解析Feed时出错。请确保   feed是有效的JSON或RSS。

对于Flash简报技巧，我无法让Alexa将我的Lambda函数返回为有效的JSON。当我在这个Lambda函数上调用API网关时，它返回有效的JSON。 为什么Alexa不会认出它？我已经阅读了feed guildlines here，并且做得很短。

import json
def lambda_handler(event, context):
    js = [ 
          {
          "uid": "EXAMPLE_CHANNEL_MULTI_ITEM_JSON_TTS_1",
          "updateDate": "2016-04-10T00:00:00.0Z",
          "titleText": "Multi Item JSON (TTS)",
          "mainText": "This channel has multiple TTS JSON items. This is the first item.",
          "redirectionUrl": "https://www.amazon.com"
         },
         {
          "uid": "EXAMPLE_CHANNEL_MULTI_ITEM_JSON_TTS_2",
          "updateDate": "2016-04-10T00:00:00.0Z",
          "titleText": "Multi Item JSON (TTS)",
          "mainText": "This channel has multiple TTS JSON items. This is the second item.",
          "redirectionUrl": "https://www.amazon.com"
         }
        ]

    js = json.dumps(js)
    return js 

返回字符串

"[{\"mainText\": \"This channel has multiple TTS JSON items. This is   the first item.\", \"redirectionUrl\": \"https://www.amazon.com\", \"uid\": \"EXAMPLE_CHANNEL_MULTI_ITEM_JSON_TTS_1\", \"titleText\": \"Multi Item JSON (TTS)\", \"updateDate\": \"2016-04-10T00:00:00.0Z\"}, {\"mainText\": \"This channel has multiple TTS JSON items. This is the second item.\", \"redirectionUrl\": \"https://www.amazon.com\", \"uid\": \"EXAMPLE_CHANNEL_MULTI_ITEM_JSON_TTS_2\", \"titleText\": \"Multi Item JSON (TTS)\", \"updateDate\": \"2016-04-10T00:00:00.0Z\"}]"

我已经过验证＆＃34;此输出使用this online tool作为有效JSON。

如果有人拥有亚马逊接受的格式正确的JSON Feed，请在下面粘贴该代码。