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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 prepare_filenames(self, normalized_url, request):
 """ Prepare template filename list based on the user authenticated state If user is authenticated user, it use '_authenticated' as a suffix. Otherwise it use '_anonymous' as a suffix to produce the template filename list. The list include original filename at the end of the list. Args: normalized_url (str):
 A normalized url request (instance):
 An instance of HttpRequest Returns: list Examples: """

        filenames = [normalized_url]
        if request.user.is_authenticated():
            filenames.insert(0, normalized_url + ".authenticated")
        else:
            filenames.insert(0, normalized_url + ".anonymous")
        return filenames