import unreal
class hoge:
def show_messageDialog(self):
title="タイトル"
message="メッセージ"
message_type=unreal.AppMsgType.OK_CANCEL
unreal.EditorDialog.show_message(title,message,message_type, default_value=unreal.AppReturnType.NO, message_category=unreal.AppMsgCategory.WARNING)
class_Ins=hoge()
hoge.show_messageDialog()
参考URL
https://docs.unrealengine.com/5.3/en-US/PythonAPI/class/EditorDialog.html#unreal.EditorDialog