docs: def _get_repeat_masker_header(pairwise_alignment):
    """generate header string of repeatmasker formated repr of self."""
    res = ""
    res += str(pairwise_alignment.meta[ALIG_SCORE_KEY]) + " "
    res += "{:.2f}".format(pairwise_alignment.meta[PCENT_SUBS_KEY]) + " "
    res += "{:.2f}".format(pairwise_alignment.meta[PCENT_S1_INDELS_KEY]) + " "
    res += "{:.2f}".format(pairwise_alignment.meta[PCENT_S2_INDELS_KEY]) + " "
    res += (pairwise_alignment.s1.name
            if (pairwise_alignment.s1.name != "" and
                pairwise_alignment.s1.name is not None)
            else UNKNOWN_SEQ_NAME) + " "
    res += str(pairwise_alignment.s1.start) + " "
    res += str(pairwise_alignment.s1.end - 1) + " "
    res += "(" + str(pairwise_alignment.s1.remaining) + ") "
    res += ("C " if not pairwise_alignment.s2.is_positive_strand() else "")
    res += (pairwise_alignment.s2.name
            if (pairwise_alignment.s2.name != "" and
                pairwise_alignment.s2.name is not None)
            else UNKNOWN_SEQ_NAME) + " "
    res += ("(" + str(pairwise_alignment.s2.remaining) + ")"
            if not pairwise_alignment.s2.is_positive_strand()
            else str(pairwise_alignment.s2.start))
    res += " "
    # Note here that we need to convert between our internal representation
    # for coordinates and the repeat-masker one; internally, we always store
    # coordinates as exclusive of the final value with start < end;
    # repeatmasker gives the larger coordinate as the 'start' when the match
    # is to the reverse complement, so we have to swap start/end, and its
    # coordinates are inclusive of end, so we have to subtract 1 from end.
    res += str(pairwise_alignment.s2.end - 1) + " "
    res += (str(pairwise_alignment.s2.start)
            if not pairwise_alignment.s2.is_positive_strand()
            else "(" + str(pairwise_alignment.s2.remaining) + ")") + " "
    res += pairwise_alignment.meta[UNKNOWN_RM_HEADER_FIELD_KEY] + " "
    res += str(pairwise_alignment.meta[RM_ID_KEY])
    return res