Add note about eager-defun compat.

samples/core/guide/autograph.ipynb

@@ -170,7 +170,9 @@
       },
       "cell_type": "markdown",
       "source": [
-        "We'll enable  [eager execution](https://www.tensorflow.org/guide/eager) for demonstration purposes, but AutoGraph works in both eager and [graph execution](https://www.tensorflow.org/guide/graphs) environments:"
+        "We'll enable  [eager execution](https://www.tensorflow.org/guide/eager) for demonstration purposes, but AutoGraph works in both eager and [graph execution](https://www.tensorflow.org/guide/graphs) environments:",
+        "",
+        "Important: The converted code will _work_ in eager mode. But it runs as an eager-python function. To run the resulting code in a graph wrap in `tf.contrib.eager.defun`."
       ]
     },
     {