docs: @Override
      public AbstractHttpEntity harvest(long generation) {
          ByteBufferEntity enty;
          try {
              m_writers.get(generation).flush();
              enty = new ByteBufferEntity(m_bbos.get(generation).toByteBuffer(), CSVContentType);
          } catch (IOException e) {
              throw new BulkException("unable to flush CSVWriter", e);
          } finally {
              m_bbos.get(generation).reset();
          }
          return enty;
      }