API Gateway Websocket Rate Limit in serverless.yml

I am trying to set up rate limits on a Websocket API Gateway in serverless.

From what I can figure out, the limit is applied by the usage plan for the account, which gets associated with stages through the API key.

Serverless Framework - AWS Lambda Events - REST API (API Gateway v1)

My project has both Websocket and REST APIs set up which appear as separate instances, but the above plan only has the REST associated with it.

There is nothing in serverless documentation about either API keys or usage plans so I don’t think it’s possible to set up rate limits this way.

Is it possible to set the rate limit for Websocket APIs either at a UsagePlan level or for individual routes?