public Id<DgCommodity> convertLinkToLinkPair2CommodityId(Id<Link> fromLinkId,Id<Link> toLinkId){
  String idString=fromLinkId + "33" + toLinkId;
  return idPool.createId(idString,DgCommodity.class);
}

public Id < DgCommodity > convertLinkToLinkPair2CommodityId ( Id < Link > fromLinkId , Id < Link > toLinkId ) { String idString = fromLinkId + "33" + toLinkId ; return idPool . createId ( idString , DgCommodity . class ) ; }
create a commodity id for the fromlink - tolink pair
