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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 deep_update_dict(default, options):
 """ Updates the values in a nested dict, while unspecified values will remain unchanged """

    for key in options.keys():
        default_setting = default.get(key)
        new_setting = options.get(key)
        if isinstance(default_setting, dict):
            deep_update_dict(default_setting, new_setting)
        else:
            default[key] = new_setting