chore: Apply Black formatting to litellm directory

[Chesars]

Title

chore: Apply Black code formatting

Relevant issues

Fixes #16283 (part 1 of 2)

Pre-Submission checklist

Please complete all items before asking a LiteLLM maintainer to review your PR

• I have Added testing in the tests/litellm/ directory, Adding at least 1 test is a hard requirement - see details
• I have added a screenshot of my new test passing locally
• My PR passes all unit tests on make test-unit
• My PR's scope is as isolated as possible, it only solves 1 specific problem

Type

🧹 Refactoring

Changes

Problem

The CI currently runs cd litellm && poetry run black . on every PR, reformatting 512 files but discarding the changes. This wastes ~59 seconds per PR.

Solution (Part 1)

This PR applies Black formatting to the litellm/ directory (512 files).

Before merge:

• CI reformats 512 files on every PR (~59 seconds wasted)
• Changes discarded, process repeats next PR

After + Part 2:

• CI verifies formatting with black --check (~1 second)
• Fails CI if code not formatted (prompts developers to format locally)
• Saves ~96 minutes per 100 PRs

What Black Does

Black applies consistent Python code formatting:

• Line length limits (88 characters by default)
• Consistent string quotes
• Standardized indentation and spacing
• PEP 8 compliant formatting

No Breaking Changes

Black preserves the AST (Abstract Syntax Tree) and only modifies code style - no functional changes.

Official guarantee: Black checks that reformatted code produces a valid AST equivalent to the original.

References: Black docs | GitHub

Changes

• Ran cd litellm && poetry run black . to format 512 files (PEP 8 compliant)
• No functional changes - Black is AST-preserving and only modifies code style
• Includes 504 core files + 8 enterprise files (via symlink in litellm/proxy/enterprise)

⚠️ Important: Merge Conflicts Warning

This PR modifies 512 files, which means:

• ⚠️ Active PRs will likely have merge conflicts when rebasing/merging after this
• ⚠️ Contributors should run cd litellm && poetry run black . locally to resolve conflicts
• ⚠️ Recommend coordinating merge timing.
• ✅ After merge, all future PRs will need Black formatting to pass CI (Part 2)

Type of Changes

• ✅ Non-breaking changes - Only code style/formatting modified
• ✅ No functional changes - Logic, behavior, and APIs remain identical
• ✅ No dependency changes - Same runtime and development dependencies
• ✅ Automated formatting - All changes made by Black formatter tool

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