class_docstr: Scenario for single document text summarization.
  Currently supports the following datasets:
  1. XSum (https://arxiv.org/pdf/1808.08745.pdf)
  2. CNN/DailyMail non-anonymized (https://arxiv.org/pdf/1704.04368.pdf)
  
  Task prompt structure
  
      Summarize the given document.
      Document: {tok_1 ... tok_n}
      Summary: {tok_1 ... tok_m}
  
  Example from XSum dataset
  
      Document: {Part of the Broad Road was closed to traffic on Sunday at about 18:00 GMT.
                 The three adults and three children have been taken to Altnagelvin Hospital
                 with non life-threatening injuries. The Fire Service, Northern Ireland Ambulance Service
                 and police attended the crash. The Broad Road has since been reopened.}
      Summary: {Three adults and three children have been taken to hospital following a crash involving
                a tractor and a campervan in Limavady, County Londonderry}
class_docstr_tok: ["Scenario","for","single","document","text","summarization",".","Currently","supports","the","following","datasets",":","1",".","XSum","(","https",":","\/\/arxiv.org\/pdf\/1808.08745.pdf",")","2",".","CNN\/DailyMail","non-anonymized","(","https",":","\/\/arxiv.org\/pdf\/1704.04368.pdf",")","Task","prompt","structure","Summarize","the","given","document",".","Document",":","{","tok_1","...","tok_n","}","Summary",":","{","tok_1","...","tok_m","}","Example","from","XSum","dataset","Document",":","{","Part","of","the","Broad","Road","was","closed","to","traffic","on","Sunday","at","about","18:00","GMT",".","The","three","adults","and","three","children","have","been","taken","to","Altnagelvin","Hospital","with","non","life-threatening","injuries",".","The","Fire","Service",",","Northern","Ireland","Ambulance","Service","and","police","attended","the","crash",".","The","Broad","Road","has","since","been","reopened",".","}","Summary",":","{","Three","adults","and","three","children","have","been","taken","to","hospital","following","a","crash","involving","a","tractor","and","a","campervan","in","Limavady",",","County","Londonderry","}"]
code: def _download_dataset(self, url, tag):
      data_dir = os.path.join(self.output_path, "data")
      ensure_directory_exists(data_dir)
      ensure_file_downloaded(
          source_url=url,
          target_path=os.path.join(data_dir, f"{tag}.pk"),
      )
  
      with open(os.path.join(data_dir, f"{tag}.pk"), "rb") as fin:
          dataset = pickle.load(fin)
  
      return dataset
  
file_path: H2O/h2o_hf/helm/src/helm/benchmark/scenarios/summarization_scenario.py
imports: import os
  import pickle
  from typing import List, Optional
  from helm.common.general import ensure_file_downloaded, ensure_directory_exists
  from .scenario import Scenario, Instance, Reference, TRAIN_SPLIT, VALID_SPLIT, TEST_SPLIT, CORRECT_TAG, Input, Output
label_desc: Use image node_id 4 for calling the SummarizationScenario obj's underlying member method code with example usage: obj._download_dataset(url, tag) and returns: dataset