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
resource = resources[resource_id]
    client = get_client(resource, func_details)
    function = getattr(client, func_details['function'])
    params = func_details.get('parameters') or lambda_get_params()
    defaults = func_details.get('defaults', {})
    if 'Properties' not in resource:
        resource['Properties'] = {}
    resource_props = resource['Properties']
    if callable(params):
        params = params(resource_props, stack_name=stack_name, resources=resources)
    else:
        params = dict(params)
        for param_key, prop_keys in dict(params).items():
            params.pop(param_key, None)
            if not isinstance(prop_keys, list):
                prop_keys = [prop_keys]
            for prop_key in prop_keys:
                if prop_key == PLACEHOLDER_RESOURCE_NAME:
                    params[param_key] = PLACEHOLDER_RESOURCE_NAME
                else:
                    if callable(prop_key):
                        prop_value = prop_key(resource_props, stack_name=stack_name, resources=resources)
                    else:
                        prop_value = resource_props.get(prop_key)
                    if prop_value is not None:
                        params[param_key] = prop_value
                        break
    
    resource_name_holder = {}
    def fix_placeholders(o, **kwargs):