code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              JavaClass cls = classContext.getJavaClass();
              if ((serializableClass != null) && cls.implementationOf(serializableClass)) {
                  super.visitClassContext(classContext);
              }
          } catch (ClassNotFoundException cnfe) {
              bugReporter.reportMissingClass(cnfe);
          }
      }
docs: overrides the method to check for Serializable