code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              stack = new OpcodeStack();
              toStringRegisters = new HashMap<>();
              packageName = classContext.getJavaClass().getPackageName();
              super.visitClassContext(classContext);
          } finally {
              stack = null;
              toStringRegisters = null;
          }
      }
docs: overrides the visitor to reset the stack
  
  @param classContext
  the context object of the currently parsed class