Abstract base class for TrainAndTestSetProducers that contains default
implementations of add/remove listener methods and defualt
visual representation.
Interface specifying routines that all weka beans should implement
in order to allow the bean environment to exercise some control over the
bean and also to allow the bean to excercise some control over connections.
Beans may want to impose constraints in terms of
the number of connections they will allow via a particular
listener interface.
Bean that can can accept batch or incremental classifier events
and produce dataset or instance events which contain instances with
predictions appended.