better way of identifying daoFactories

lib/dialects/abstract/query-generator.js

 var Utils = require("../../utils")
 var Utils = require("../../utils")
   , SqlString = require("../../sql-string")
   , SqlString = require("../../sql-string")
+  , daoFactory = require("../../dao-factory")
 
 
 module.exports = (function() {
 module.exports = (function() {
   var QueryGenerator = {
   var QueryGenerator = {
@@ -364,7 +365,7 @@ module.exports = (function() {
             break
             break
           }
           }
 
 
-          if (!Utils._.isPlainObject(item)) {
+          if (item instanceof daoFactory) {
             item = {model: item}
             item = {model: item}
           }
           }