private WordItem singleStemSegment(Item blockAsItem, String stem, String indexName,
                                       Substring substring) {
        WordItem replacement = new WordItem(stem, indexName, true, substring);
        replacement.setStemmed(true);
        copyAttributes(blockAsItem, replacement);
        return replacement;
    }
Replaces query terms with their stems

@author Mathias Lidal
@author bratseth
@author Steinar Knutsen
container-search/src/main/java/com/yahoo/prelude/querytransform/StemmingSearcher.java