private List<List<Line>> splitChangeSet(List<Line> remainingMessage)
      throws BatchDeserializerException {

    final HeaderField contentTypeField = headers.getHeaderField(HttpHeader.CONTENT_TYPE);
    final String changeSetBoundary =
        BatchParserCommon.getBoundary(
            contentTypeField.getValue(), contentTypeField.getLineNumber());
    validateChangeSetBoundary(changeSetBoundary, headers);

    return BatchParserCommon.splitMessageByBoundary(remainingMessage, changeSetBoundary);
  }