static discard ({ stmtId = NO_STATEMENT_ID, n = FETCH_ALL } = {}) {
    const metadata = buildStreamMetadata(
      stmtId === null || stmtId === undefined ? NO_STATEMENT_ID : stmtId,
      n || FETCH_ALL
    )
    return new RequestMessage(
      DISCARD,
      [metadata],
      () => `DISCARD ${json.stringify(metadata)}`
    )
  }
Generates a new DISCARD message with additional metadata.
@param {Integer|number} stmtId
@param {Integer|number} n
@return {RequestMessage} the PULL message.