docs: def get_dataset(corpora):
      """
      Return a dictionary of subjectID -> [path_to_resource].
      """
      # TODO: make filter methods for the files
  
      def make_posix_path(dirpath, filename):
          dirpath = posixpath.sep.join(dirpath.split(os.sep))
          return posixpath.join(dirpath, filename)
  
      wav_files_in_corpora = filter(
          lambda x: x.endswith('.wav'),
          sum(
              [list(map(lambda x: make_posix_path(corpus, x), os.listdir(corpus))) for corpus in corpora],
              []
          ),
      )
  
      dataset = {}
      for wav_file in wav_files_in_corpora:
          subjectID = os.path.split(wav_file)[-1].split('.')[0].split('_')[0]
  
          if subjectID in dataset:
              dataset[subjectID].append(wav_file)
          else:
              dataset[subjectID] = [wav_file]
  
      return dataset