```ruby
class ListSerializer < ActiveModel::Serializer
  # embed :ids, include: true
  attributes :id, :title
  has_many :list_items
end
```

Add description filed to list serializer.
user
```ruby
class ListSerializer < ActiveModel::Serializer
  # embed :ids, include: true
  attributes :id, :title, :description, :user
  has_many :list_items
end
```
assistant