     @static
     @return {Array}
     ###
+    @_modelProps: undefined
     @getModelProps: ->
 
         if not @_modelProps?

        return props


    ###
    properties to cache, private.
    ###
    @_propOfCreatedAt: undefined 
    @_propOfUpdatedAt: undefined
    @_modelProps: undefined



    ###*
    get prop name whose type is CREATED_AT
    notice: only one prop should be enrolled to CREATED_AT

    @static
    @return {String} propName
    ###
    @_propOfUpdatedAt: undefined
    @getPropOfUpdatedAt: ->

        if @_propOfUpdatedAt is undefined
