public boolean override(String indexName, String command, ImmutableSDField field) {
            if (schema == null) {
                return false;
            }

            Index index = schema.getIndex(indexName);
            if (index == null) {
                return false;
            }

            Stemming indexStemming = index.getStemming();
            if (indexStemming == null) {
                return false;
            }

            if ( ! Stemming.NONE.equals(indexStemming)) {
                owner.addIndexCommand(indexName, CMD_STEM + ":" + indexStemming.toStemMode());
            }
            return true;
        }
Override the setting of this index for this field, returns true if overriden, false if this index should be
set according to the field
config-model/src/main/java/com/yahoo/schema/derived/IndexInfo.java