I am using the **latest** localstack docker image to test aws s3, lambda and cloudformation locally. s3 and lambda seems to be working fine but when I call cloudformation **create-stack** api it gives me a 502 BadGateway error. This is the command I am using

`aws cloudformation create-stack \
  --template-body template.yaml \
  --stack-name cfn-test \
  --parameters ParameterKey=BucketPrefix,ParameterValue=demo-bucket \
  --endpoint-url=http://localhost:4581`

This is the error I get:
`An error occurred (502) when calling the CreateStack operation (reached max retries: 4): Bad Gateway`

From docker logs I got the following error
`2019-12-31T22:12:09:ERROR:localstack.services.generic_proxy: Error forwarding request: 'str' object has no attribute 'get' Traceback (most recent call last):
  File "/opt/code/localstack/localstack/services/generic_proxy.py", line 242, in forward
    path=path, data=data, headers=forward_headers)
  File "/opt/code/localstack/localstack/services/cloudformation/cloudformation_listener.py", line 164, in forward_request
    modified_request = transform_template(req_data)
  File "/opt/code/localstack/localstack/services/cloudformation/cloudformation_listener.py", line 83, in transform_template
    if parsed.get('Transform') == 'AWS::Serverless-2016-10-31':
AttributeError: 'str' object has no attribute 'get'`

Although, when I try the **list-stacks** api it seems to be working fine
`aws --endpoint-url=http://localhost:4581 cloudformation list-stacks`

`{
    "StackSummaries": []
}`

`2019-12-31 22:10:51,865:API: 127.0.0.1 - - [31/Dec/2019 22:10:51] "GET / HTTP/1.1" 200 -`

I could not find a solution in any of the past issues or anywhere on the internet. Please assist
kwargs = {
            'restApiId': props['RestApiId'],
            'resourceId': props['ResourceId'],
            'httpMethod': props['HttpMethod'],
            'requestParameters': props.get('RequestParameters')
        }
        if integration:
            kwargs['type'] = integration['Type']
            kwargs['integrationHttpMethod'] = integration.get('IntegrationHttpMethod')
            kwargs['uri'] = integration.get('Uri')
            return client.put_integration(**kwargs)
        kwargs['authorizationType'] = props.get('AuthorizationType')
        return client.put_method(**kwargs)
def fix_account_id_in_arns(params):
    def fix_ids(o, **kwargs):
        if isinstance(o, dict):
            for k, v in o.items():
                if common.is_string(v, exclude_binary=True):
                    o[k] = aws_stack.fix_account_id_in_arns(v)
        elif common.is_string(o, exclude_binary=True):
            o = aws_stack.fix_account_id_in_arns(o)
        return o
    result = common.recurse_object(params, fix_ids)
    return result
def convert_data_types(func_details, params):
    """ Convert data types in the "params" object, with the type defs
        specified in the 'types' attribute of "func_details". """
    types = func_details.get('types') or {}
    attr_names = types.keys() or []
    def cast(_obj, _type):