[Experimental - do not merge] Test extensibility

[vkozyura]

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ danjoa
✅ nkaputnik
❌ vkozyura
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