Refactor test files for improved readability and consistency

- Removed unnecessary blank lines and adjusted formatting in test files.
- Ensured consistent use of commas in function calls and assertions across various test cases.
- Updated import statements for better organization and clarity.
- Enhanced mock setups in tests for better isolation and reliability.
- Improved assertions to follow a consistent style for better readability.

app/models/extraction.py

@@ -1,6 +1,6 @@
 from typing import TYPE_CHECKING
 
-from sqlmodel import Field, Relationship, UniqueConstraint
+from sqlmodel import Field, Relationship
 
 from app.models.base import BaseModel