code: public void setLogo(String url) {
          if (url != null && url.trim().length() > 0) {
              if (Url.isUrl(url) || url.startsWith("data:image/")) {
                  this.logo = url.trim();
              } else {
                  throw new IllegalArgumentException(url + " is not a valid URL.");
              }
          }
      }
docs: Sets the URL of an image representing a logo.
  
  @param url   a URL as a String