Clarify the tf.function tracing rules for custom classes

PiperOrigin-RevId: 551287285

Author: tensorflower-gardener

site/en/guide/function.ipynb

@@ -371,7 +371,11 @@
         "* For Python ordered containers such as `list` and `tuple`, etc., the type is parameterized by the types of their elements; for example, the type of `[1, 2]` is `ListTraceType<LiteralTraceType<1>, LiteralTraceType<2>>` and the type for   `[2, 1]` is `ListTraceType<LiteralTraceType<2>, LiteralTraceType<1>>` which is different.\n",
         "* For Python mappings such as `dict`, the type is also a mapping from the same keys but to the types of values instead the actual values. For example, the type of `{1: 2, 3: 4}`, is `MappingTraceType<<KeyValue<1, LiteralTraceType<2>>>, <KeyValue<3, LiteralTraceType<4>>>>`. However, unlike ordered containers, `{1: 2, 3: 4}` and `{3: 4, 1: 2}` have equivalent types.\n",
         "* For Python objects which implement the `__tf_tracing_type__` method, the type is whatever that method returns\n",
-        "* For any other Python objects, the type is a generic `TraceType` which uses the object's Python equality and hashing for matching. (Note: It relies on [weakref](https://docs.python.org/3/library/weakref.html) to the object and hence only works as long as the object is in scope/not deleted.)\n"
+        "* For any other Python objects, the type is a generic `TraceType`, its matching precedure is:\n",
+        "  * First it checks if the object is the same object used in the previous trace (using python `id()` or `is`). Note that this will still match if the object has changed, so if you use python objects as `tf.function` arguments it's best to use *immutable* ones.\n",
+        "  * Next it checks if the object is equal to the object used in the previous trace (using python `==`).\n",
+        "      \n",
+        "  Note that this procedure only keeps a [weakref](https://docs.python.org/3/library/weakref.html) to the object and hence only works as long as the object is in scope/not deleted.)\n"
       ]
     },
     {