code: def _read_dataset_metadata(self):
      
      blob = self.storage_client.get_blob(
          'dataset/' + self.dataset_name + '_dataset.csv')
      buf = BytesIO()
      blob.download_to_file(buf)
      buf.seek(0)
      return eval_lib.DatasetMetadata(buf)
docs: Reads dataset metadata.
  
      Returns:
        instance of DatasetMetadata