setslice of ``[0:0]`` correctly, which in particular could occur
when using ``insert(0, item)`` with the association proxy.  Due
to some quirk in Python collections, the issue was much more likely
with Python 3 rather than 2.  Also in 0.8.3, 0.7.11.
[ticket:2807]

Conflicts:
	doc/build/changelog/changelog_09.rst

method, which fires off each time the collection is associated
or de-associated with a mapped object - the decorator
was not tested or functional.  The decorator method
is now named :meth:`.collection.linker` though the name "link"
remains for backwards compatibility.  Courtesy Luca Wehrstedt.
[ticket:2653]

collections, mainly that the usage of the @collection decorators
will now honor the __mro__ of the given class, applying the
logic of the sub-most classes' version of a particular collection
method.   Previously, it wasn't predictable when subclassing
an existing instrumented class such as :class:`.MappedCollection`
whether or not custom methods would resolve correctly.
[ticket:2654]

- The undocumented (and hopefully unused) system of producing
custom collections using an ``__instrumentation__`` datastructure
associated with the collection has been removed, as this was a complex
and untested feature which was also essentially redundant versus the
decorator approach.   Other internal simplifcations to the
orm.collections module have been made as well.

- Fixes to the "dynamic" loader on :func:`.relationship`, includes
that backrefs will work properly even when autoflush is disabled,
history events are more accurate in scenarios where multiple add/remove
of the same object occurs, as can often be the case in conjunction
with the association proxy.  [ticket:2637]

now generates attribute events.  Previously, a None
append would be ignored in some cases.  Related
to [ticket:2229].

- [feature] The presence of None in a mapped collection
now raises an error during flush.   Previously,
None values in collections would be silently ignored.
[ticket:2229]

    to an instrumented collection is no longer
    associated with the parent class due to
    expiration/attribute refresh/collection
    replacement, but an append
    or remove operation is received on the
    now-detached collection.  [ticket:2476]