code: def val_gen(self) -> Optional[CalamariDataGeneratorParams]:
      return None
  
file_path: calamari/calamari_ocr/ocr/training/pipeline_params.py
imports: from copy import deepcopy
  from dataclasses import dataclass, field
  from random import shuffle
  from typing import Optional
  import logging
  from paiargparse import pai_dataclass, pai_meta
  from tfaip import TrainerPipelineParams, TrainerPipelineParamsBase, PipelineMode
  from calamari_ocr.ocr.dataset.datareader.base import CalamariDataGeneratorParams
  from calamari_ocr.ocr.dataset.datareader.file import FileDataParams
  from calamari_ocr.ocr.dataset.datareader.pagexml.reader import PageXML
  from calamari_ocr.ocr.dataset.params import DATA_GENERATOR_CHOICES
label_desc: Use image node_id 2 for calling the CalamariTrainOnlyPipelineParams obj's underlying member method code with example usage: obj.val_gen() and returns: None