I'm having problems updating a recently-imported SNS TopicPolicy. I'm getting the less-then-helpful error InvalidParameter: Invalid parameter: Policy Error: null. Since the only field I'm updating is the policy doc, I'm guessing the error is there. I'm guessing the format of the doc based on IAM policy docs, so maybe I'm making mistakes. Is there an example of creating an SNS TopicPolcy in Pulumi anywhere? Or a spec for TopicPolicy policy documents?