[BEAM-8575] Windows idempotency: Applying the same window fn (or wind… (#10071)
[BEAM-8575] Windows idempotency: Applying the same window fn (or wind… (#10071)

* [BEAM-8575] Windows idempotency: Applying the same window fn (or window fn + GBK) to the
input multiple times will have the same effect as applying it once

* Update sdks/python/apache_beam/transforms/window_test.py

Co-Authored-By: Lukasz Cwik <a1559536771c19c1fd82195b5338c890b9c1c3e7@google.com>

* Update sdks/python/apache_beam/transforms/window_test.py

Co-Authored-By: Lukasz Cwik <a1559536771c19c1fd82195b5338c890b9c1c3e7@google.com>

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