This module provides a semiring for generating parse trees lazily in best-first
order, based on the algorithm of Huang and Chiang . Unlike their method
however, this needs no preassigned limit on the number of parses to produce.
 Liang Huang and David Chiang. Better k-best parsing.
In Proceedings of the Ninth International Workshop on Parsing Technology, pages 53–64.
Association for Computational Linguistics, 2005.
- graph_nviterbi(+G:graph, +P:sw_params, -T:expl_tree, -LP:number) is nondet
- Find the most probable parse tree, and then find progressively less probable
parse trees on backtracking.