Challenge 3: The Same Logging Context Manager with contextlib — Possible Solution
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from contextlib import contextmanager

@contextmanager
def log_section(name):
    print(f"Entering {name}")
    try:
        yield
    finally:
        print(f"Exiting {name}")

with log_section("data processing"):
    print("doing work...")
    print("still working...")

Output:
Entering data processing
doing work...
still working...
Exiting data processing

WHY THIS WORKS AS AN ANSWER
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@contextmanager above def log_section(name): reuses this chapter's own
timer() example structure exactly — turning an ordinary generator
function into a full context manager, with none of Challenge 2's
__init__/__enter__/__exit__ boilerplate.

Code written BEFORE yield — here, print(f"Entering {name}") — becomes
the __enter__ logic, running the moment the with block starts, per
this chapter's own explanation of how @contextmanager maps generator
code onto the two dunder methods.

yield itself (with no value, since this challenge's with statement
doesn't use as x:) is where the with block's own body actually runs —
the two print("...") calls happen at this exact point, reusing the
same "the code pauses at yield and resumes later" mechanic from
generators (Course 2, Chapter 5).

Wrapping yield in try/finally reuses this chapter's own timer()
example precisely, and for the same reason: finally guarantees
print(f"Exiting {name}") runs even if an exception occurred inside the
with block, matching the class-based version's own guarantee from
Challenge 2 that __exit__ always runs. This produces identical output
to Challenge 2's LogSection class, just written as a much shorter
generator function instead of a full class with two separate dunder
methods — directly demonstrating the boilerplate trade-off this
chapter's own comparison called out.