public boolean isIndexable() {
        return switch (this) {
            case ALPHABETIC, NUMERIC, INDEXABLE_SYMBOL -> true;
            default -> false;
        };
    }
Marker for whether this type of token can be indexed for search.
Note that a Token can be excluded from an index, even though the token type marks
it as indexable.

@see com.yahoo.language.process.Token#isIndexable()
@return whether this type of token can be indexed
linguistics/src/main/java/com/yahoo/language/process/TokenType.java