1. pages_controller.rb

   ...

  def index
    render @blogs, shallow: true
  end

  ...

2. blog_serializer.rb

class BlogSerializer < ActiveModel::Serializer
  attributes :id, :title
  has_many :posts
  
  def posts_serializer_options
    if @options[:shallow]
      { hide_comments: true  }
    end
  end
end

3. post_serializer.rb

class PostSerializer < ActiveModel::Serializer
  attributes :id, :title, :body
  has_many :comments
  
  def include_comments?
    !@options[:hide_comments]
  end
end

4. comment_serializer.rb

class CommentSerializer < ActiveModel::Serializer
  attributes :id, :body
end