Documentation for valid PATCH payload for annotations on hypothes.is?

[Matthew Lincoln]

I'm trying to update the permissions for a given annotation hosted on https://hypothes.is, and it's unclear how to do this from the documentation at https://h.readthedocs.io/en/latest/api-reference/v1/#tag/annotations/paths/~1annotations~1{id}/patch

Sending a PATCH request to the appropriate URI with the payload

{"permissions": {'read': ['group:__world__'], 'admin': ['acct:$ACCT_NAME'], 'update': ['acct:$ACCT_NAME'], 'delete': ['acct:$ACCT_NAME']}}

returns a 400, {'status': 'failure', 'reason': 'Expected a valid JSON payload, but none was found!'}

Is it possible to update permissions for an annotation like so?