docs: public URI changesUri(Map<String, Object> query) {
  
          //lets find the since parameter
          if(query.containsKey("since")){
              Object since = query.get("since");
              if(!(since instanceof String)){
                  //json encode the seq number since it isn't a string
                  Gson gson = new Gson();
                  query.put("since",gson.toJson(since));
              }
          }
          return this.path("_changes").query(query).build();
      }