produces the negation of the expression "IN" returns
when used against an empty collection.  Also in 0.8.3.

this is a dictionary where applications can store arbitrary
data local to a :class:`.Session`.
The contents of :attr:`.Session.info` can be also be initialized
using the ``info`` argument of :class:`.Session` or
:class:`.sessionmaker`.

Hanno Schlichting.  Also in 0.8.3, 0.7.11.
[ticket:2791]

used only as an ``alias()`` construct, it would not render using the
WITH keyword.  Also in 0.8.3, 0.7.11.
[ticket:2783]

any supported CPython 2 or 3 environment. [ticket:2161]

if the given target/event/fn is set up to listen.
- repair mutable package which is doing some conditional event listening

provided via the :func:`.event.remove` function.
[ticket:2268]
- reorganization of event.py module into a package; with the addition of the
docstring work as well as the new registry for removal, there's a lot more code now.
the package separates concerns and provides a top-level doc for each subsection
of functionality
- the remove feature works by providing the EventKey object which associates
the user-provided arguments to listen() with a global, weak-referencing registry.
This registry stores a collection of _ListenerCollection and _DispatchDescriptor
objects associated with each set of arguments, as well as the wrapped function
which was applied to that collection.  The EventKey can then be recreated for
a removal, all the _ListenerCollection and _DispatchDescriptor objects are located,
and the correct wrapped function is removed from each one.