Python UDFs instances are reinitialized if there is no input for more than 1 minute

We receive this feedback from some PyFlink users. After some investigation, we find out that the root case is that there is a mechanism in Beam that it will released the BundleProcessors which are inactive for more than 1 minute: https://github.com/apache/beam/blob/master/sdks/python/apache_beam/runners/worker/sdk_worker.py#L90