fix token calculate error,if cached_tokens is None

[LAB422PanTong]

when i use crewAi，find the bug ，if cached_tokens is None，sum_cached_prompt_tokens will error

[joaomdmoura]

Disclaimer: This review was made by a crew of AI Agents.

Code Review Comment for PR #2152

Overview

This pull request addresses a critical bug in token_counter_callback.py that improves the calculation of tokens by ensuring cached_tokens is checked for existence before processing. The enhancement aims to provide a more robust handling of token calculations to prevent runtime errors.

Code Quality Findings

1. Bug Fix Validation: The addition of the condition to check cached_tokens significantly reduces the risk of null reference errors. This was a necessary change and immediately addresses the issue at hand.

   # After
   if hasattr(usage, "prompt_tokens_details") and usage.prompt_tokens_details and usage.prompt_tokens_details.cached_tokens:

2. Code Readability: The method currently employs chained conditions which could be clearer. This can be rectified using defensive programming patterns that enhance understandability and maintainability.

3. Missing Type Hints: The omission of type hints diminishes code clarity. Explicit type annotations would assist future developers in understanding data structures and catching potential issues early in development.

4. Comment Clarity: Documentation within the code is minimal. Adding descriptive comments around critical checks can improve maintainability and make the codebase more navigable for devs unfamiliar with the repo.

Suggested Improvements

1. Defensive Programming Style:
   Implement a utility function to safely access nested properties, simplifying null checks. Here's an example:

   def safe_get_attr(obj, attr, default=None):
       return getattr(obj, attr, default) if obj else default

   Then use it in your method:

   prompt_tokens_details = safe_get_attr(usage, 'prompt_tokens_details')
   cached_tokens = safe_get_attr(prompt_tokens_details, 'cached_tokens')

2. Add Type Hints:
   Enhance code clarity by adding type hints in your method definition:

   from typing import Optional, Any
   
   def log_success_event(
           self, 
           usage: Optional[TokenUsage], 
           **kwargs: Any
   ) -> None:

3. Commenting Logic:
   Add comments explaining each block of logic:

   # Check if usage object contains valid tokens details before processing

Historical Context and Related Practices

In similar past pull requests, issues involving nullable types often led to runtime exceptions. For example, previous improvements in the token_cost_process.py have included similar defensive checks to reinforce reliability. This suggests implementing similar strategies across related files could ensure continuity in error handling and function robustness.

Implications for Related Files

• token_cost_process.py: Ensure that summing operations are safeguarded against null values, especially in recent changes related to caching.
• usage.py: Review for consistent handling of token-related data structures, possibly implementing similar utility methods for safer property access.

Summary

The current changes to token_counter_callback.py effectively tackle the immediate bug regarding cached_tokens. However, integrating the suggested improvements would substantially enhance code quality, readability, and maintainability. Considering additional tests tailored for token calculations will also play a vital role in safeguarding the integrity of the application in future updates.

The low-risk level associated with these changes suggests that thorough testing of these adjustments in conjunction with existing unit tests should suffice to validate the functionality without introducing undue burden on development time.

By adhering to these recommendations, we can ensure a more stable and maintainable codebase moving forward. Thank you for your efforts in addressing this important issue!