private List<FieldPart> ensureTokenized() {
        if (tokenizedContent == null) {
            tokenizeContent();
        }
        return tokenizedContent;
    }
Get a list representation of the tokens in the content. This is
only a copy, changes here will not affect the HitField.

@return a list containing the content in tokenized form.
container-search/src/main/java/com/yahoo/prelude/hitfield/HitField.java