give warning message about the type cast

Author: xieguigang

R#/Runtime/Internal/objects/dataset/pipeline.vb

@@ -308,7 +308,7 @@ Namespace Runtime.Internal.Object
                 ElseIf GetType(T).IsInterface AndAlso DirectCast(upstream, pipeline).elementType.raw.ImplementInterface(Of T) Then
                     Return upstream
                 ElseIf DirectCast(upstream, pipeline).elementType Is RType.any Then
-                    Call "the given upstream pipeline is a stream of generic object collection".Warning
+                    Call "the given upstream pipeline is a stream of generic object collection. some type cast maybe failure!".Warning
                     Return upstream
                 Else
                     Return Message.InCompatibleType(GetType(T), DirectCast(upstream, pipeline).elementType.raw, env,