public class TopNGramRecord
This class stores the best K ngrams for each class for a model. It
does so by keeping priority queues of the best K trees seen,
The interface is not too advanced at the moment. To use, first
create it with the number of classes and the counts of the ngrams,
and then add trees one at a time with countTree. The results can
be extracted with toString(). There is no way to directly access
the internal results.