class_docstr: A no-op wrapper of datasets and signatures.
  
  Example usage:
  
  ```python
  train_dataset = tf.data.Dataset(...)
  valid_dataset = tf.data.Dataset(...)
  dataset_builder = NullDatasetBuilder(train_dataset, valid_dataset)
  ```
class_docstr_tok: ["A","no-op","wrapper","of","datasets","and","signatures",".","Example","usage",":","``","`","python","train_dataset","=","tf.data.Dataset","(","...",")","valid_dataset","=","tf.data.Dataset","(","...",")","dataset_builder","=","NullDatasetBuilder","(","train_dataset",",","valid_dataset",")","``","`"]
docstr: See `AbstractDatasetBuilder`.
code: def build_valid_dataset(self, *arg, **kwargs) -> tf.data.Dataset:
      """See `AbstractDatasetBuilder`."""
      return self._valid_dataset
  
imports: import abc
  import dataclasses
  import os
  from typing import Any, Dict, List, Optional, Tuple, Union
  import tensorflow
  from tensorflow_ranking.python import data
  from tensorflow_ranking.python.keras import losses
  from tensorflow_ranking.python.keras import metrics
  from tensorflow_ranking.python.keras import model
  from tensorflow_ranking.python.keras import saved_model
  from tensorflow_ranking.python.keras import strategy_utils
label_desc: Use image node_id 3 for calling the NullDatasetBuilder obj's underlying member method code with example usage: obj.build_valid_dataset() and returns: self