code: private static MethodHandles.Lookup lookupIn(final Class<?> declaringClass) {
  
          try {
              final Constructor<MethodHandles.Lookup> constructor = MethodHandles.Lookup.class.getDeclaredConstructor(
                      Class.class,
                      int.class);
              constructor.setAccessible(true);
              return constructor.newInstance(declaringClass, MethodHandles.Lookup.PRIVATE);
          } catch (NoSuchMethodException | InvocationTargetException | InstantiationException | IllegalAccessException e) {
              throw new RuntimeException(e);
          }
  
      }
docs: Creates a method lookup that is capable of accessing private members of declaring classes this Mixin factory has
  usually no access to.
  
  @param declaringClass
  @return
  @throws NoSuchMethodException
  @throws IllegalAccessException
  @throws InvocationTargetException
  @throws InstantiationException