What header file do I include to access UUserWidget?

Same as the title:
What header file do I include to access UUserWidget?

#How to Extend UserWidget in C++

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#include "Runtime/UMG/Public/UMG.h"
#include "Runtime/UMG/Public/UMGStyle.h"
#include "Runtime/UMG/Public/Slate/SObjectWidget.h"
#include "Runtime/UMG/Public/IUMGModule.h"
#include "Runtime/UMG/Public/Blueprint/UserWidget.h"

See tutorial for full details including required build cs additions of UMG,Slate, SlateCore

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