Providing arguments to transactions in Datastore Plus (NDB)

I'm having trouble working out how to pass in arguments into transactions when using Datastore Plus.

Could someone please rewrite this regular-datastore example code?

from google.appengine.ext import db

class Accumulato开发者_Python百科r(db.Model):
    counter = db.IntegerProperty()

def increment_counter(key, amount):
    obj = db.get(key)
    obj.counter += amount
    obj.put()

q = db.GqlQuery("SELECT * FROM Accumulator")
acc = q.get()

db.run_in_transaction(increment_counter, acc.key(), 5)

I'm particularly interested in the datastore plus equivalent of that last line.

The datastore plus documentation's example code doesn't deal with arguments at all (hardcoded inside the transaction).

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Assuming you can follow the example from the docs, the answer is to use a lambda (or a named helper function). E.g.

yield context.transaction(lambda: increment_counter(acc.key(), 5))