- Restart-Safe Primitives:
  - If you follow everything shown up to this point then your primitive is already "restart-safe."
  - Primitives that violate the rules may NOT be "restart-safe." Some examples of possible problems:
    - Opening or closing files outside of `open()` and `close()`.
    - Failure to do initialization inside `open()`.
    - Failure to close all pipes in the `close()` method.
    - Having own processing loop in addition to that of `process()`.