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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 get_bundles():
 """ Used to cache the bundle definitions rather than loading from config every time they're used """

    global _cached_bundles

    if not _cached_bundles:
        _cached_bundles = BundleManager()

        for bundle_conf in bundles_settings.BUNDLES:
            _cached_bundles[bundle_conf[0]] = Bundle(bundle_conf)

    return _cached_bundles