code: def download_shared_files(job, samples, config):
      
      job.fileStore.logToMaster('Downloaded shared files')
      file_names = ['reference', 'phase', 'mills', 'dbsnp', 'cosmic']
      urls = [config.reference, config.phase, config.mills, config.dbsnp, config.cosmic]
      for name, url in zip(file_names, urls):
          if url:
              vars(config)[name] = job.addChildJobFn(download_url_job, url=url).rv()
      job.addFollowOnJobFn(reference_preprocessing, samples, config)
docs: Downloads files shared by all samples in the pipeline
  
      :param JobFunctionWrappingJob job: passed automatically by Toil
      :param Namespace config: Argparse Namespace object containing argument inputs
      :param list[list] samples: A nested list of samples containing sample information