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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def exec_event(event, webhooks, payload):
 """Execute event. Merge webhooks run set to do some stats after all of the webhooks been responded successfully. +---------+ +---------+ | | +---------+ | +---------+ +------+-----+ |merge runset+------> +---------+ +------+-----+ +---------+ | | +---------+ | +---------+ Error webhook will be propagated. Note that other webhook calls will still execute. """

    calls = (
        call_webhook.s(event, webhook, payload)
        for webhook in webhooks
    )
    callback = merge_webhooks_runset.s()

    call_promise = chord(calls)
    promise = call_promise(callback)
    return promise