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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 _namespace_default():
 """ Get current namespace if running in a k8s cluster If not in a k8s cluster with service accounts enabled, default to 'default' Taken from https://github.com/jupyterhub/kubespawner/blob/master/kubespawner/spawner.py#L125 """

    ns_path = '/var/run/secrets/kubernetes.io/serviceaccount/namespace'
    if os.path.exists(ns_path):
        with open(ns_path) as f:
            return f.read().strip()
    return 'default'