[huuan26]

Summary

This PR improves type annotations in requests.adapters:

1. Replaced all Incomplete occurrences in HTTPAdapter:
   • __attrs__: list[str] (runtime: list of attribute names).
   • config: dict[str, Any] (runtime: configuration dictionary).
   • proxy_manager: dict[str, ProxyManager | SOCKSProxyManager] (runtime: dict mapping proxy URLs to proxy managers).
   • poolmanager: PoolManager (runtime: urllib3.poolmanager.PoolManager instance).
2. Clarified HTTPAdapter.proxy_manager_for return type from Any to ProxyManager | SOCKSProxyManager.
3. Fully typed untyped parameters and return type for HTTPAdapter.cert_verify.
4. Removed unused from _typeshed import Incomplete.
5. Added assert_type tests in stubs/requests/@tests/test_cases/check_adapters.py.

Verification

• flake8 --config .flake8 stubs/requests: passed (0 errors)
• ruff check stubs/requests: passed (0 errors)
• tests/regr_test.py requests: passed across test cases with mypy
• tests/stubtest_third_party.py requests: passed (success against installed requests 2.34.2)
• tests/check_typeshed_structure.py: passed

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉