code: def get_validation_image_text_data_iter(data_loader: RawParallelDatasetLoader,
                                          validation_source_root: str,
                                          validation_source: str,
                                          validation_target: str,
                                          buckets: List[Tuple[int, int]],
                                          bucket_batch_sizes: List[BucketBatchSize],
                                          source_image_size: tuple,
                                          vocab_target: vocab.Vocab,
                                          max_seq_len_target: int,
                                          batch_size: int,
                                          use_feature_loader: bool = False,
                                          preload_features: bool = False) -> 'ParallelSampleIter':
      
      logger.info("=================================")
      logger.info("Creating validation data iterator")
      logger.info("=================================")
  
      validation_source_images = [FileListReader(validation_source, validation_source_root)]
      validation_target_sentences = SequenceReader(validation_target, vocab_target, add_bos=True, limit=None)
  
      validation_data_statistics = get_data_statistics(source_readers=None,
                                                       target_reader=validation_target_sentences,
                                                       buckets=buckets,
                                                       length_ratio_mean=1.0,
                                                       length_ratio_std=1.0,
                                                       source_vocabs=None,
                                                       target_vocab=vocab_target)
      validation_data_statistics.log(bucket_batch_sizes)
  
      validation_data = data_loader.load(validation_source_images[0],
                                         validation_target_sentences,
                                         validation_data_statistics.num_sents_per_bucket).fill_up(bucket_batch_sizes)
      return ImageTextSampleIter(data=validation_data,
                                 buckets=buckets,
                                 batch_size=batch_size,
                                 bucket_batch_sizes=bucket_batch_sizes,
                                 image_size=source_image_size,
                                 use_feature_loader=use_feature_loader,
                                 preload_features=preload_features)
docs: Returns a ParallelSampleIter for the validation data.