kinds of internal column loader options within internal logging.
fixes #3539

which indicates to the ORM that a positive set of None should be
persisted as the value NULL, instead of omitting the column from
the INSERT statement.  This feature is used both as part of the
implementation for :ticket:`3514` as well as a standalone feature
available on any type.  fixes #3250
- add new documentation section illustrating the "how to force null"
 use case of #3250
- alter our change from #3514 so that the class-level flag is now
called "should_evaluate_none"; so that "evaluates_none" is now
a generative method.

to use mapper.cascade_iterator() for this purpose as it was not really
designed for that use case.  Add docs to cascade_iterator() pointing
to the recipe.  fixes #3498

:meth:`.Session.bulk_save_objects` and related bulk methods have
been scaled back to the extent that this functionality is not
currently used, e.g. checks for column default values to be
fetched after an INSERT or UPDATE statement.
fixes #3526

column that had some kind of "fetch on update" value and was not
locally present in the given object would cause an AttributeError
within the operation.
fixes #3525

unambiguous tracking of all object lifecycle state transitions
in terms of the :class:`.Session` itself, e.g. pending,
transient,  persistent, detached.   The state of the object
within each event is also defined.
fixes #2677
- Added a new session lifecycle state :term:`deleted`.  This new state
represents an object that has been deleted from the :term:`persistent`
state and will move to the :term:`detached` state once the transaction
is committed.  This resolves the long-standing issue that objects
which were deleted existed in a gray area between persistent and
detached.   The :attr:`.InstanceState.persistent` accessor will
**no longer** report on a deleted object as persistent; the
:attr:`.InstanceState.deleted` accessor will instead be True for
these objects, until they become detached.
- The :paramref:`.Session.weak_identity_map` parameter is deprecated.
See the new recipe at :ref:`session_referencing_behavior` for
an event-based approach to maintaining strong identity map behavior.
references #3517

detailing ORM event recipes across the board.