Use Field(default_factory=...) for mutable defaults in Lemma model

[mzargham]

Summary

The Lemma model in symproof/models.py uses bare mutable defaults for two fields:

• Line 385: assumptions: dict[str, dict] = {}
• Line 418: depends_on: list[str] = []

Impact

The model has frozen=True and Pydantic v2 internally copies defaults, so this is not a runtime bug. However, it violates Python best practice, will trigger linting warnings, and could confuse contributors.

Fix

from pydantic import Field

assumptions: dict[str, dict] = Field(default_factory=dict)
depends_on: list[str] = Field(default_factory=list)

Files

• symproof/models.py:385,418