class_docstr: From https://github.com/UCSD-AI4H/COVID-Dialogue, "COVID-Dialogue-Dataset-English is an English medical dialogue
  dataset about COVID-19 and other types of pneumonia. Patients who are concerned that they may be infected by
  COVID-19 or other pneumonia consult doctors and doctors provide advice. There are 603 consultations. Each
  consultation consists of ID, URL, Description of patient’s medical condition and Dialogue."
  
  The following is an example a patient-doctor interaction from the dataset:
  
  patient: i have all the symptoms except fever, i went to medicross and dr said i can get tested if i want to i'm
  not sure if i should. she gave me antibiotics klacid xl 500mg, she said i can take it if i feel worse i'm worried
  it will make immune system bad?
  
  in brief: antibiotic i don't recommend antibiotics for a simple viral upper respiratory tract infection unless
  examination revealed signs of acute bronchitis or sinusitis. they are not effective for viral infections like
  covid 19 with no bacterial lung involvement either. if you've been exposed to someone with covid 19 or or if you
  or someone you were exposed to travelled to a region where it was endemic, get tested would you like to video
  or text chat with me?
  
  @article{ju2020CovidDialog,
    title={CovidDialog: Medical Dialogue Datasets about COVID-19},
    author={Ju, Zeqian and Chakravorty, Subrato and He, Xuehai and Chen, Shu and Yang, Xingyi and Xie, Pengtao},
    journal={ https://github.com/UCSD-AI4H/COVID-Dialogue},
    year={2020}
  }
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docstr: Build `Instance`s using the questions asked by concerned patients and the responses by doctors.
docstr_tok: ["Build","`","Instance","`","s","using","the","questions","asked","by","concerned","patients","and","the","responses","by","doctors","."]
code: def get_instances(self) -> List[Instance]:
      """
      Build `Instance`s using the questions asked by concerned patients and the responses by doctors.
      """
  
      def download_and_read_lines(file_name: str) -> List[str]:
          file_path: str = os.path.join(data_path, file_name)
          ensure_file_downloaded(
              source_url=COVIDDialogScenario.SOURCE_URL_TEMPLATE.format(
                  file_name=file_name
              ),
              target_path=file_path,
              unpack=False,
          )
  
          with open(file_path) as f:
              return f.read().splitlines()
  
      data_path: str = os.path.join(self.output_path, "data")
      ensure_directory_exists(data_path)
  
      instances: List[Instance] = []
      for split in ALL_SPLITS:
          dataset_split: str = "val" if split == VALID_SPLIT else split
  
          # The files with the questions end with ".source"
          questions: List[str] = download_and_read_lines(
              f"{dataset_split}.source"
          )
  
          # The files with the responses end with ".target"
          responses: List[str] = download_and_read_lines(
              f"{dataset_split}.target"
          )
  
          for question, response in zip(questions, responses):
              # Questions in the dataset are already prepended with "patient:".
              # Remove those and add it via `input_prefix` of `AdapterSpec`.
              question = question.replace("patient: ", "")
              instances.append(
                  Instance(
                      input=Input(text=question),
                      references=[
                          Reference(
                              output=Output(text=response),
                              tags=[CORRECT_TAG],
                          )
                      ],
                      split=split,
                  )
              )
  
      return instances
  
imports: import os
  from typing import List
  from helm.common.general import ensure_directory_exists, ensure_file_downloaded
  from .scenario import Scenario, Instance, Reference, ALL_SPLITS, CORRECT_TAG, VALID_SPLIT, Input, Output
label_desc: Use image node_id 1 for calling the COVIDDialogScenario obj's underlying member method code with example usage: obj.get_instances() and returns: instances, f