code: public static void setMessageAccountId(Message sqsMessage, String s3ObjectKey) {
          if (!sqsMessage.getAttributes().containsKey(SourceAttributeKeys.ACCOUNT_ID.getAttributeKey())) {
              String accountId = extractAccountIdFromObjectKey(s3ObjectKey);
              if (accountId != null) {
                  sqsMessage.addAttributesEntry(SourceAttributeKeys.ACCOUNT_ID.getAttributeKey(), accountId);
              }
          }
      }
docs: Add the account ID attribute to the <code>sqsMessage</code> if it does not exist.
  @param sqsMessage The SQS message.
  @param s3ObjectKey The S3 object key.