It shall be unlawful to use any screen, blind, curtain, partition, article, or other device in the windows or upon the doors of any retail liquor establishment which will have the effect of preventing a clear view into the interior of such licensed premise from the street, road, or sidewalk at all times. All licensed premises shall be continuously lighted during business hours by natural or artificial white lights to insure the clear visibility into said establishment. Any licensee who willfully violates the provisions of this section shall be subject to a revocation of his license by the Municipality as provided herein. (Ref. 53-167 RS Neb.)