docs: public String getCodeSource(ProtectionDomain pd) {
  
          CodeSource cs = pd.getCodeSource();
  
          String csStr = null;
  
          if (cs == null) {
  
              csStr = "null code source";
          } else {
  
              URL url = cs.getLocation();
  
              if (url == null) {
  
                  csStr = "null code URL";
              } else {
  
                  csStr = url.toString();
              }
  
          }
  
          return csStr;
      }