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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_backends():
 """Retrieve the list of configured service backends."""

    backends = []
    backend_paths = getattr(
        settings, 'MAMA_CAS_SERVICE_BACKENDS',
        ['mama_cas.services.backends.SettingsBackend']
    )
    for backend_path in backend_paths:
        backend = import_string(backend_path)()
        backends.append(backend)
    return backends