code: def build_datasets(self, cfg):
      datasets = super().build_datasets(cfg)
  
      # get validation dataset name
      val_ds_name = []
      for name, d in datasets.items():
          if self.split in d:
              val_ds_name.append(name)
      if not val_ds_name:
          return datasets  # no validation sets
      assert (
          len(val_ds_name) == 1
      ), "Only support one dataset for validation"
      val_ds_name = val_ds_name[0]
  
      # get question file, annotation file and anwser list in COCO format
      if self.annotation_file == None:
          if (
              "coco" not in val_ds_name
          ):  # coco is already precomputed in dataset
              self.annotation_file = os.path.join(
                  registry.get_path("cache_root"),
                  f"{val_ds_name}_gt",
                  f"{val_ds_name}_{self.split}_annotations.json",
              )
              if get_rank() == 0:
                  os.makedirs(
                      os.path.join(
                          registry.get_path("cache_root"),
                          f"{val_ds_name}_gt",
                      ),
                      exist_ok=True,
                  )
                  convert_to_coco_gt(
                      datasets[val_ds_name],
                      self.annotation_file,
                      self.caption_key,
                      self.sample_id_key,
                      self.split,
                      load_gt_from_file=self.load_gt_from_file,
                      img_ids=self.img_ids,
                  )
      return datasets
  
imports: import json
  import os
  import pandas
  from tqdm import tqdm
  from lavis.common.dist_utils import main_process, get_rank
  from lavis.common.registry import registry
  from lavis.tasks.base_task import BaseTask
  from lavis.common.utils import is_convertible_to_int, is_url, cache_url
  from pycocoevalcap.eval import COCOEvalCap
  from pycocotools.coco import COCO
  from torchvision.datasets.utils import download_url
label_desc: Use image node_id 3 for calling the CaptionTask obj's underlying member method code with example usage: obj.build_datasets(cfg) and returns: datasets, datasets