refactor(agents): Improve transfer type safety

[mdabydeen]

Created branch refactor/agent-transfer-typing and implemented the typing cleanup in src/google/ adk/flows/llm_flows/agent_transfer.py

Changes:

• Replaced Any with BaseAgent.
• Accepted Sequence[BaseAgent].
• Corrected type-only imports.
• Removed obsolete TODOs and quoted annotations.

[rohityan]

Hi @mdabydeen , Thank you for your contribution! We appreciate you taking the time to submit this pull request.
Can you please clarify the changes.

[mdabydeen]

Hey @rohityan, appreciate you taking the time.

This PR is a small, low-risk typing cleanup in agent_transfer.py There's no behavior changes.

What changed:

• Replaced loose Any types with the actual BaseAgent type for transfer target parameters.
• Changed list[...] to Sequence[...] where the code only reads the collection, better reflecting intent.
• Cleaned up TYPE_CHECKING imports to reference concrete modules (agents.base_agent, agents.llm_agent) instead of package-level re-exports.
• Removed quoted forward-ref strings ('LlmAgent', 'BaseAgent') now that from future import annotations makes them unnecessary
• Deleted two stale # TODO: Refactor the annotation comments that this change resolves. these functions previously accepted Any, so type checkers couldn't catch misuse of target_agent/target_agents. Now ca and the docstrings match reality instead of describing a duck-typed contract.

Risk: none functionally, this is annotations and imports only, no runtime logic touched.

[adk-bot]

Response from ADK Triaging Agent

Hello @mdabydeen, thank you for creating this PR!

This PR is a code refactoring of type annotations. Could you please include a testing plan section in your PR description describing how you have verified these changes (e.g., summary of mypy or pytest results)? If there is an associated GitHub issue for this, please link it in your description as well.

This will help our reviewers verify the correctness of the refactoring. Thank you!