perf: Defer black import to first use

[KRRT7]

Stack: 2/4 — depends on #231. Merge #231 first, then this PR.

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• Defer import black from module level to first use in answers.py and utils.py
• black (code formatter + transitive deps: pathspec, black.nodes, etc.) loaded on every import typeagent but only used in two cold formatting paths

black.format_str() is called in two places:

• create_context_prompt() in knowpro/answers.py — formats debug context for LLM prompts
• format_code() in aitools/utils.py — developer pretty-print utility

Neither runs during normal library operation. Moving the import inside each function eliminates ~78ms of transitive module loading from the import chain.

Benchmark

Azure Standard_D2s_v5 — 2 vCPU, 8 GiB RAM, Python 3.13

Import Time (hyperfine, warmup 5, min-runs 30)

Benchmark	Before	After	Speedup
import typeagent	791 ms ± 11 ms	713 ms ± 8 ms	1.11x

Offline E2E Test Suite (hyperfine, warmup 2, min-runs 10)

Benchmark	Before	After	Speedup
69 offline tests	5.72 s ± 90 ms	5.60 s ± 98 ms	1.02x

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Generated by codeflash optimization agent

[gvanrossum]

Should have one this a long time ago. :-(

[KRRT7]

Thanks, wasn't sure you wanted import time optimizations, if you do, I have a few more ready to go.

[gvanrossum]

This one is dear to my heart because I wish we could remove black from the mandatory dependencies. Happy to review more.

[KRRT7]

why can't you remove black? out of curiousness

[gvanrossum]

why can't you remove black? out of curiousness

I could, but it gives the nicest formatted expressions when doing hardcore debugging. What we could do is import it conditionally and just use repr() if black cannot be imported. Then we can remove it from the main deps. Developers have the dev tools installed (pyright, black, isort, pytest, etc.) and will see the black-formatted debug output.

[KRRT7]

Went ahead and did this — #235 replaces black.format_str with pprint.pformat + ast.literal_eval in both call sites (stdlib only, no conditional imports). Moved black from dependencies to the dev dependency-group so make format/make check still work but library consumers don't pull it in.