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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_extension(self, app):
 """Initialize cache instance."""

        app.config.setdefault('CACHE_VERSION', '0')
        app.config.setdefault('CACHE_PREFIX', 'r')
        app.config.setdefault('CACHE_BACKEND', 'rio.exts.flask_cache.NullBackend')
        app.config.setdefault('CACHE_BACKEND_OPTIONS', {})