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