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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_app():
 """return bottle app that includes all sub-apps"""

    from bottle import default_app
    default_app.push()
    for module in ("mongo_orchestration.apps.servers",
                   "mongo_orchestration.apps.replica_sets",
                   "mongo_orchestration.apps.sharded_clusters"):
        __import__(module)
    app = default_app.pop()
    return app