fix: resolve mypy type checking errors in client.py

[sasa-ken]

Use typing.Any for fallback imports instead of None to avoid:

• 'Cannot assign to a type' errors
• 'Name already defined' redefinition warnings
• Incompatible type assignment issues

Add type: ignore comment for the fallback assignment.

Description

Fixes #

Type of Change

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to change)
• Documentation update
• Protocol specification change
• Refactoring (no functional changes)
• CI/tooling improvement

Changes Made

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• All existing tests pass

Test results:

<!-- Paste test output here -->

Documentation

• Documentation updated (if needed)
• Examples updated (if API changed)
• CHANGELOG.md updated (for user-facing changes)
• API documentation generated/updated

Protocol Changes

• Protocol version bumped (if breaking)
• Backward compatibility analyzed
• All SDKs updated to match
• Migration guide provided (if breaking)

Checklist

• Code follows project style guidelines
• Self-review completed
• Comments added for complex logic
• No new warnings introduced
• Tests added/updated and passing
• Documentation updated (if needed)
• No server/node code added (SDK repo only!)
• SPDX headers present in new files
• Commit messages follow Conventional Commits
• Ready for review

SDK-Specific Checks

Rust SDK

• cargo fmt --check passes
• cargo clippy passes (no warnings)
• cargo test passes
• Cargo.toml version updated (if needed)

JavaScript/TypeScript SDK

• npm run lint passes
• npm run build succeeds
• npm test passes
• Type definitions updated

Python SDK

• black --check . passes
• mypy type checking passes
• pytest passes
• Version updated in pyproject.toml (if needed)

Breaking Changes

Additional Notes

Screenshots/Logs