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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 app_start(device_id, app_id):
 """ Starts an app with corresponding package name"""

    if not is_valid_app_id(app_id):
        abort(403)
    if not is_valid_device_id(device_id):
        abort(403)
    if device_id not in devices:
        abort(404)

    success = devices[device_id].launch_app(app_id)
    return jsonify(success=success)