```ruby
class PostSweeper < ActionController::Caching::Sweeper
  observe CrowdblogCore::Post

  def after_create(post)
    expire_all(post)
  end

  def after_update(post)
    expire_all(post)
  end

  def after_destroy(post)
    expire_all(post)
  end

  private
  def expire_all(post)
    if post.published?
      expire_page(controller: '/posts', action: 'index')
      expire_page(controller: '/posts', action: 'show',
                  year: post.year, month: post.month, day: post.day, id: post.permalink, format: 'html')
      expire_page atom_feed_path(format: 'xml')
    end
    expire_page preview_path(post.to_param)
  end
end
```

Remove sweeper code, let the implementation to be done in the container app
user
```ruby
class PostSweeper < ActionController::Caching::Sweeper
  observe CrowdblogCore::Post

  # Implement it in your base app!
end
```
assistant