code: public void onSuccess (final WriteResponse response) {
      for (final Thunk thunk: this.thunks) {
        thunk.callback.onSuccess(new WriteResponse() {
          @Override
          public Object getRawResponse() {
            return response.getRawResponse();
          }
  
          @Override
          public String getStringResponse() {
            return response.getStringResponse();
          }
  
          @Override
          public long bytesWritten() {
            return thunk.sizeInBytes;
          }
        });
      }
    }
docs: After batch is sent and get acknowledged successfully, this method will be invoked