code: @Nonnull
    public CSSURI setURI (@Nonnull final String sURI)
    {
      ValueEnforcer.notNull (sURI, "URI");
      if (CSSURLHelper.isURLValue (sURI))
        throw new IllegalArgumentException ("Only the URI and not the CSS-URI value must be passed!");
  
      m_sURI = sURI;
      return this;
    }
docs: Set the URI string of this object. This may either be a regular URI or a
  data URL string (starting with "data:"). The passed string may not start
  with the prefix "url(" and end with ")".
  
  @param sURI
  The URI to be set. May not be <code>null</code> but may be empty
  (even though an empty URL usually does not make sense).
  @return this