code: function UpdateGSet(options, callback) {
      var gset_opts = {
          additions: options.additions
      };
      delete options.additions;
  
      UpdateSetBase.call(this, options, callback);
  
      var self = this;
      Joi.validate(gset_opts, schema, function(err, opts) {
          if (err) {
              throw err;
          }
          self.additions = opts.additions;
      });
  }
docs: Provides the Update GSet class, its builder, and its response.
  @module CRDT
   
  Command used tp update a gset in Riak
  
  As a convenience, a builder class is provided:
  
  var update = new UpdateGSet.Builder()
  .withBucketType('gsets')
  .withBucket('myBucket')
  .withKey('set_1')
  .withAdditions(['this', 'that', 'other'])
  .withCallback(callback)
  .build();
  
  See {{#crossLink "UpdateSet.Builder"}}UpdateSet.Builder{{/crossLink}}
  @class UpdateGSet
  @constructor
  @param {String[]|Buffer[]} [options.additions] The values to be added to the set.
  @extends UpdateSetBase