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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def loadFromFile(fileName):
 """ load the configuration for the ReturnInfo from a fileName @param fileName: filename that contains the json configuration to use in the ReturnInfo """

        assert os.path.exists(fileName), "File " + fileName + " does not exist"
        conf = json.load(open(fileName))
        return ReturnInfo(
            articleInfo=ArticleInfoFlags(**conf.get("articleInfo", {})),
            eventInfo=EventInfoFlags(**conf.get("eventInfo", {})),
            sourceInfo=SourceInfoFlags(**conf.get("sourceInfo", {})),
            categoryInfo=CategoryInfoFlags(**conf.get("categoryInfo", {})),
            conceptInfo=ConceptInfoFlags(**conf.get("conceptInfo", {})),
            locationInfo=LocationInfoFlags(**conf.get("locationInfo", {})),
            storyInfo=StoryInfoFlags(**conf.get("storyInfo", {})),
            conceptClassInfo=ConceptClassInfoFlags(**conf.get("conceptClassInfo", {})),
            conceptFolderInfo=ConceptFolderInfoFlags(**conf.get("conceptFolderInfo", {}))
        )