How to use the pouchdb-mapreduce-utils.callbackify function in pouchdb-mapreduce-utils

opts = {};
    }
    opts = opts ? coerceOptions(opts) : {};

    if (typeof fun === 'function') {
      fun = {map : fun};
    }

    var promise = Promise.resolve().then(function () {
      return queryPromised(db, fun, opts);
    });
    promisedCallback(promise, callback);
    return promise;
  }

  var abstractViewCleanup = callbackify(function () {
    var db = this;
    /* istanbul ignore next */
    if (typeof db._viewCleanup === 'function') {
      return customViewCleanup(db);
    }
    if (isRemote(db)) {
      return httpViewCleanup(db);
    }
    return localViewCleanup(db);
  });

  return {
    query: abstractQuery,
    viewCleanup: abstractViewCleanup
  };
}