code: public void createChunks(String frameKey, byte[] expectedTypes, int chunkId, int totalNumRows, int[] maxVecSizes) throws IOException {
          ab.put1(ExternalFrameHandler.INIT_BYTE);
          ab.put1(ExternalFrameHandler.CREATE_FRAME);
          ab.putStr(frameKey);
          this.expectedTypes = expectedTypes;
          ab.putA1(expectedTypes);
          ab.putA4(maxVecSizes);
          ab.putInt(totalNumRows);
          ab.putInt(chunkId);
          writeToChannel(ab, channel);
      }
docs: Create chunks on the h2o backend. This method creates chunk in en empty frame.
  @param frameKey name of the frame
  @param expectedTypes expected types
  @param chunkId chunk index
  @param totalNumRows total number of rows which is about to be sent