- [feature] The Session will produce warnings

  - [feature] The Session will produce warnings
    when unsupported methods are used inside the
    "execute" portion of the flush.   These are
    the familiar methods add(), delete(), etc.
    as well as collection and related-object
    manipulations, as called within mapper-level
    flush events
    like after_insert(), after_update(), etc.
    It's been prominently documented for a long
    time that  SQLAlchemy cannot guarantee
    results when the Session is manipulated within
    the execution of the flush plan,
    however users are still doing it, so now
    there's a warning.   Maybe someday the Session
    will be enhanced to support these operations
    inside of the flush, but for now, results
    can't be guaranteed.