code: function TransactionOptions(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 TransactionOptions.
  @memberof google.firestore.v1
  @interface ITransactionOptions
  @property {google.firestore.v1.TransactionOptions.IReadOnly|null} [readOnly] TransactionOptions readOnly
  @property {google.firestore.v1.TransactionOptions.IReadWrite|null} [readWrite] TransactionOptions readWrite
   
  Constructs a new TransactionOptions.
  @memberof google.firestore.v1
  @classdesc Represents a TransactionOptions.
  @implements ITransactionOptions
  @constructor
  @param {google.firestore.v1.ITransactionOptions=} [properties] Properties to set