Use this callback to instantiate the ICENode and register your
custom ICENode. Although user data is stored in the ICENode context
during the BeginEvaluate
callback, it can also be set during the Init callback and then
accessed later in the Evaluate callback.
| Note |
The user data stored in BeginEvaluate or
Init is always accessible from the Evaluate callback. However, unless
the custom node threading mode is single-threading, the Context::PutUserData
property cannot be used from the Evaluate callback. |