Python 到 Appsync 解析器 Dynamo 更新

Question

我有一些 python 代码更新了我的 object，它附加了一个带有项目的列表：

    table = dynamodb.Table('Table')

    param = [{"name": "parameter 3", "att": "stuff"}, {"name": "parameter 4", "att": "more stuff"}]

    response = table.update_item(
        Key={
            'id': '2b05bf49-952c-43b5-8458-002e68c21de3'
        },
        UpdateExpression="SET #p = list_append(#p, :vals)",

        ExpressionAttributeValues={
            ':vals': param,
        },
        ExpressionAttributeNames={
            '#p': "parameter_list",
        },

        ReturnValues="UPDATED_NEW"
    )

现在我正在尝试在 AppSync 解析器中做同样的事情。

{
  "version": "2017-02-28",
  "operation": "UpdateItem",
  "key": {
    "id": $util.dynamodb.toDynamoDBJson($ctx.args.input.thingId),
  },

  ## Set up some space to keep track of things we're updating **

  #set( $expNames = {"#p": "new_parameters"} )
  #set( $input = [{"name": "parameter 3", "att": "stuff"}, {"name": "parameter 4", "att": "more stuff"}])
  #set( $expValues = {":vals": $util.dynamodb.toDynamoDB($input) })

  "update": {
    "expression": "SET #p = list_append(#p, :vals)",
    "expressionNames": $utils.toJson($expNames),
    "expressionValues" : $expValues
  },

}

但是，我不断收到此错误：

Encountered \"#set\" at velocity[line 14, column 3]\nWas expecting one of:\n    <RPAREN> ...\n    \"-\" ...\n    \"+\" ...\n    \"*\" ...\n    \"/\" ...\n    \"%\" ...\n    <LOGICAL_AND> ...\n    <LOGICAL_OR> ...\n    <LOGICAL_LT> ...\n    <LOGICAL_LE> ...\n    <LOGICAL_GT> ...\n    <LOGICAL_GE> ...\n    <LOGICAL_EQUALS> ...\n    <LOGICAL_NOT_EQUALS> ...\n    

任何人都有一个想法如何解决这个问题？ 非常感谢