code: public static Query withFieldValues(String field,
                                          NaryOp op,
                                          String rfield) {
          Query q = new Query(false);
          q.add("field", field).add("op", op.toString()).add("rfield", rfield);
          return q;
      }
docs: <pre>
  { field: <field>, op: <in/nin>, rfield: <rfield> }
  </pre>