How does TaskGroup handle cancellation and ExceptionGroup?

Question presented to candidate: "Inside async with asyncio.TaskGroup(), one child task raises. Walk me through exactly what happens next: to the other children, to the code in the async with body, and to the exception you finally see. Then: what if the whole thing is cancelled from outside, or wrapped in a timeout?"

What a strong answer should cover:

• On the first child failure the group cancels every other running child and the parent task running the body, then waits for all of them, including their finally / cleanup code, before leaving the block.
• The result is one ExceptionGroup("unhandled errors in a TaskGroup", [...]) holding every non-cancellation error (children and body); CancelledErrors of the cancelled children are not included. Handle it with except*.
• The group cancels the parent with cancel() and undoes it with uncancel() in __aexit__, so its own cancellation turns into the group error, while a real outside cancellation still comes out as a plain CancelledError (and asyncio.timeout turns it into TimeoutError).
• A child that swallows CancelledError breaks the contract: it keeps running cleanup or returns normally; always re-raise.
• KeyboardInterrupt and SystemExit are treated specially (re-raised as-is, not grouped); nested groups stay nested.

Clarifying questions expected:

• Should one failing child really stop the others, or are some children "best effort"?

Code / implementation expected: Optional — a TaskGroup where one child fails and another prints when it is cancelled, caught with except*.