<!--
title: Standardize version transitions
domain: app-frameworks
topic: Configurations
language: Python
source: fastapi/fastapi
updated: 2025-06-28
url: https://awesomereviewers.com/reviewers/fastapi-standardize-version-transitions/
-->

When supporting multiple library versions or preparing for version deprecation in configuration-dependent code, use standardized TODO comments with consistent formatting. Always include a space after the # symbol and use the prefix "TODO:" to ensure comments can be found with standard search tools.

Example:
```python
def pydantic_snapshot(
    *,
    v2: Snapshot,
    v1: Snapshot,  # TODO: remove v1 argument when deprecating Pydantic v1
):
    # Version-specific implementation
    if PYDANTIC_V2:
        return v2
    else:
        return v1
```

This practice helps teams track configuration-dependent code that will require updates during dependency upgrades, making version transitions smoother and more systematic. It also ensures that version-specific code paths are clearly documented and can be easily located when performing major configuration changes.