How to use the marklogic.patchBuilder function in marklogic

var mlclient = require('marklogic');
var qb = mlclient.queryBuilder;
var pb = mlclient.patchBuilder;
var meta = require('./meta');
var util = libRequire('db-client/util');

var funcs = {};
var moment = require('moment-timezone');
// funcs.exploreSearch = require('./exploreSearch');
funcs.patch = require('./patch');

funcs.search = function (spec) {
  // TODO: should really be supporting the txid param
  // query function wants an args list so we use apply since we
  // are dynamically creating values out of what is specified
  // console.log(require('util').inspect(this));
  // console.log(JSON.stringify(spec));
  return this.documents.query.apply(
    this,

* you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at 
 * 
 *    http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and 
 * limitations under the License. 
 */ 

var Promise = require('bluebird');
var mlclient = require('marklogic');
var qb = mlclient.queryBuilder;
var pb = mlclient.patchBuilder;
var _ = require('lodash');
var uuid = require('node-uuid');

var db;
var questionsDir = '/questions/';
var contributorPrefix = 'com.marklogic.samplestack.domain.Contributor';
var contributorDir = contributorPrefix + '/';
// TODO: pull contributor info from session
var contributorId = 'cf99542d-f024-4478-a6dc-7e723a51b040';
var contributorDisplayName = 'JoeUser';
var contributorUserName = 'joe@example.com';

var commentTemplate = {
  'owner': {
    'id': contributorId,
    'displayName': contributorDisplayName,

* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

var mlclient = require('marklogic');
var qb = mlclient.queryBuilder;
var pb = mlclient.patchBuilder;
var meta = require('./meta');
var util = libRequire('db-client/util');

var funcs = {};

/**
 * Handle an update to a contributor's reputation by patch the document.
 *
 * @param  {String} txid The transaction ID.
 * @param  {String} id The contributor ID.
 * @param  {Number} repChange Increment or decrement value.
 * @return {Promise} A promise object.
 */
funcs.patchReputation = function (txid, id, repChange) {
  // add (or subtract) from reputation property
  return this.documents.patch({

* Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at 
 * 
 *    http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and 
 * limitations under the License. 
 */ 

var mlclient = require('marklogic');
var qb = mlclient.queryBuilder;
var pb = mlclient.patchBuilder;
var meta = require('./meta');
var util = libRequire('db-client/util');
var errs = libRequire('errors');
var moment = require('moment-timezone');
var Promise = require('bluebird');

var qnaDoc = require('./index');

module.exports = function (txid, spec) {
  var self = this;

  /**
   * Handles an upvote or downvote for a Samplestack question or answer.
   * Performs three patch operations:
   *   1. Adds the contributor ID to the array of upvoters or
   *      downvoters.