Persistent Objects Base Class

The `persistent` library provides a base class, `Persistent`, for creating translucent persistent Python objects. These objects can track their their own 'dirty' state, indicating when they have been modified and need to be saved by an external persistence layer (e.g., ZODB). It is a fundamental component for building object persistence systems. The current version is 6.5, with major releases typically aligning with Python version support updates and addressing core behavior changes.