# Author: Sandeep Belgavi. Synthetic exercise; no network or provider calls.
import hashlib,json
def digest(action):return hashlib.sha256(json.dumps(action,sort_keys=True).encode()).hexdigest()
action={"tenant":"a","operation":"refund","order":"7","amount":100}
approved=digest(action)
def permit(tenant,proposal,approval):
    return proposal["tenant"]==tenant and digest(proposal)==approval
assert permit("a",action,approved)
assert not permit("b",action,approved)
assert not permit("a",dict(action,amount=1000),approved)
print("approved action accepted; other tenant and changed amount denied")