public Builder addDefaultModel(Path model) {
            addModel(Language.UNKNOWN, model);
            return this;
        }
Adds the model that will be used if the language is unknown, OR only one model is specified.
The same as addModel(Language.UNKNOWN, model).
linguistics-components/src/main/java/com/yahoo/language/sentencepiece/SentencePieceEmbedder.java