code: @Override
      public void visitClassContext(ClassContext clsContext) {
  
          try {
              stack = new OpcodeStack();
              clsVersion = clsContext.getJavaClass().getMajor();
              unendedZLIBs = new HashMap<>();
              super.visitClassContext(clsContext);
          } finally {
              unendedZLIBs = null;
              stack = null;
          }
      }
docs: implements the visitor to create and tear down the opcode stack
  
  @param clsContext the context object of the currently parsed class