Container to hold the metric for a model as scored on a specific frame.
The MetricBuilder class is used in a hot inner-loop of a Big Data pass, and
when given a class-distribution, can be used to compute CM's, and AUC's "on
the fly" during ModelBuilding - or after-the-fact with a Model and a new
Frame to be scored.
High-quality 64-bit checksum of the content of the
object. Similar to hashcode(), but a long to reduce the
chance of hash clashes. For composite objects this should
be defined using the subcomponents' checksums (or hashcodes
if not available). If two Keyed objects have the same
checksum() there should be a 1 - 1/2^64 chance that they
are the same object by value.