One option may be to post-process the JSON output:
>>> encoded = jsonpickle.encode(p, unpicklable=False)
>>> data = json.loads(encoded)
>>> del data['_sa_instance_state'] if '_sa_instance_state' in data
This is a bit of a pain, thus another option may be to write a custom
handler (BaseHandler subclass) that deletes the _sa_instance_state:
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