Internal data structure.
Eleve storages used two tries (one to model the language left-to-right and one right-to-left). It may be useful to use these tries directly. For instance if you need a model in only one direction.
Memory and disk tries are provided. As for storages, the reference implementation is provided by :class:`eleve.memory.MemoryTrie`.
The Leveldb trie have the same API. Refer to the source code for more information.