a class member is found in the documents and missing from the code

Hi everybody, I wanted to use the class FAnimSingleNodeInstanceProxy but I found it missing the member FAnimNode_SingleNode FAnimSingleNodeInstanceProxy::SingleNode from the file AnimSingleNodeInstanceProxy.h while it’s found in the API’s online document as a protected member variable (SingleNode | Unreal Engine Documentation)

Moreover when I search for the type FAnimNode_SingleNode in the solution explorer I don’t find any results.

Seems still there:

/** The internal anim node that does our processing */
FAnimNode_SingleNode SingleNode;