rangePairToCfiPair(cfiBase, rangePair) {
    var startRange = rangePair.start;
    var endRange = rangePair.end;
    startRange.collapse(true);
    endRange.collapse(false);
    let startCfi = new _epubcfi__WEBPACK_IMPORTED_MODULE_0__[/* default */ "a"](startRange, cfiBase).toString();
    let endCfi = new _epubcfi__WEBPACK_IMPORTED_MODULE_0__[/* default */ "a"](endRange, cfiBase).toString();
    return {
      start: startCfi,
      end: endCfi
    };
  }
Turn a pair of ranges into a pair of CFIs
@private
@param {string} cfiBase base string for an EpubCFI
@param {object} rangePair { start: Range, end: Range }
@return {object} { start: "epubcfi(...)", end: "epubcfi(...)" }