code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              JavaClass cls = classContext.getJavaClass();
              if (isSingleton(cls)) {
                  syncBlockBranchResetValues = new HashMap<>();
                  stack = new OpcodeStack();
                  super.visitClassContext(classContext);
              }
          } finally {
              syncBlockBranchResetValues = null;
              stack = null;
          }
      }
docs: implements the visitor to look for classes that are singletons
  
  @param classContext
  the context object of the currently parsed class