static UpdateByQuery of(Query query, Map<Expression, Object> values) {
      Preconditions.checkArgument(!values.isEmpty(), "no values");
      return ImmutableUpdateByQuery.of(query, values);
    }
If current operation is replace, return replacement, otherwise return empty optional.
Replace means override whole record / document not a subset of attributes.
criteria/common/src/org/immutables/criteria/backend/StandardOperations.java