public int encode(ByteBuffer buffer) {
        return MapEncoder.encodeMap("feature", features, buffer);
    }
Prepares this for encoding, not for external use. See encode on Query for details.
<p>
If the query feature is found in the rank feature set,
remove all these entries and insert them into the rank property set instead.
We want to hide from the user that the query feature value is sent down as a rank property
and picked up by the query feature executor in the backend.
container-search/src/main/java/com/yahoo/search/query/ranking/RankFeatures.java