docs: def index_repeatmasker_alignment_by_id(fh, out_fh, vebrose=False):
    """Build an index for a repeat-masker alignment file by repeat-masker ID."""
    def extract_UID(rm_alignment):
      return rm_alignment.meta[multipleAlignment.RM_ID_KEY]
  
    index = IndexedFile(fh, repeat_masker_alignment_iterator, extract_UID)
    index.write_index(out_fh)