code: def _clean_rec_name(rec):
      
      out_id = []
      for char in list(rec.id):
          if char in ALLOWED_CONTIG_NAME_CHARS:
              out_id.append(char)
          else:
              out_id.append("_")
      rec.id = "".join(out_id)
      rec.description = ""
      return rec
docs: Clean illegal characters in input fasta file which cause problems downstream.