function ifBreak(breakContents, flatContents, opts) {
    opts = opts || {};

    return {
      type: "if-break",
      breakContents,
      flatContents,
      groupId: opts.groupId
    };
  }
@param {Doc} [breakContents]
@param {Doc} [flatContents]
@param {object} [opts] - TBD ???
@returns Doc