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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 init_default(self):
 """ Initializes object with its default values Tries to load self.default_filename from default data directory. For safety, filename is reset to None so that it doesn't point to the original file. """

        import f311
        if self.default_filename is None:
            raise RuntimeError("Class '{}' has no default filename".format(self.__class__.__name__))
        fullpath = f311.get_default_data_path(self.default_filename, class_=self.__class__)
        self.load(fullpath)
        self.filename = None