static parseRange(rangeString) {
    const matches = /([0-9]+)-([0-9]+)/.exec(rangeString);

    if (!matches) {
      return null;
    }

    const start = Number(matches[1]);
    if (!isFinite(start)) {
      return null;
    }

    const end = Number(matches[2]);
    if (!isFinite(end)) {
      return null;
    }

    return {start: start, end: end};
  }
Parses a range string.
@param {string} rangeString The range string, e.g., "101-9213".
@return {?{start: number, end: number}} The parsed range on success;
  otherwise, return null.