code: public static String[] transactionTags(String scope, String stream, String transactionId) {
          return new String[] {TAG_SCOPE, scope, TAG_STREAM, stream, TAG_TRANSACTION, transactionId};
      }
docs: Generate transaction tags (string array) on the input scope, stream and transactionId to be associated with a metric.
  @param scope scope of the stream.
  @param stream stream name.
  @param transactionId transaction id.
  @return string array as transaction tag of metric.