code: def _get_contigs_to_use(self, contigs_to_use):
          '''If contigs_to_use is a set, returns that set. If it's None, returns an empty set.
          Otherwise, assumes it's a file name, and gets names from the file'''
          if type(contigs_to_use) == set:
              return contigs_to_use
          elif contigs_to_use is None:
              return set()
          else:
              f = pyfastaq.utils.open_file_read(contigs_to_use)
              contigs_to_use = set([line.rstrip() for line in f])
              pyfastaq.utils.close(f)
              return contigs_to_usf _get_contigs_to_use(self, contigs_to_use):
          '''If contigs_to_use is a set, returns that set. If it's None, returns an empty set.
          Otherwise, assumes it's a file name, and gets names from the file'''
          if type(contigs_to_use) == set:
              return contigs_to_use
          elif contigs_to_use is None:
              return set()
          else:
              f = pyfastaq.utils.open_file_read(contigs_to_use)
              contigs_to_use = set([line.rstrip() for line in f])
              pyfastaq.utils.close(f)
              return contigs_to_use
docs: If contigs_to_use is a set, returns that set. If it's None, returns an empty set.
          Otherwise, assumes it's a file name, and gets names from the file