docs: public Map<String, Object> asMap() {
          Map<String, Object> map = getBody().asMap();
          // add meta properties: ID, rev, deleted
          map.put("_id", id);
          if (revision != null) {
              map.put("_rev", revision);
          }
          if (this.isDeleted()) {
              map.put("_deleted", true);
          }
          return map;
      }