public StemMode toStemMode() {
        switch(this) {
            case SHORTEST: return StemMode.SHORTEST;
            case MULTIPLE: return StemMode.ALL;
            case BEST : return StemMode.BEST;
            case NONE: return StemMode.NONE;
            default: throw new IllegalStateException("Inconvertible stem mode " + this);
        }
    }
Returns the stemming object for the given string.
The legal stemming names are the stemming constants in any capitalization.

@throws IllegalArgumentException if there is no stemming type with the given name
config-model/src/main/java/com/yahoo/schema/document/Stemming.java