code: function RollbackRequest(properties) {
                      if (properties)
                          for (var keys = Object.keys(properties), i = 0; i < keys.length; ++i)
                              if (properties[keys[i]] != null)
                                  this[keys[i]] = properties[keys[i]];
                  }
docs: Properties of a RollbackRequest.
  @memberof google.firestore.v1
  @interface IRollbackRequest
  @property {string|null} [database] RollbackRequest database
  @property {Uint8Array|null} [transaction] RollbackRequest transaction
   
  Constructs a new RollbackRequest.
  @memberof google.firestore.v1
  @classdesc Represents a RollbackRequest.
  @implements IRollbackRequest
  @constructor
  @param {google.firestore.v1.IRollbackRequest=} [properties] Properties to set