You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: callouts.rb
    path of file: ./repos/truffleruby/bench/asciidoctor/asciidoctor/lib/asciidoctor
    
    the code of the file until where you have to start completion: # encoding: UTF-8
module Asciidoctor
# Public: Maintains
    
  def read_next_id
    id = nil
    list = current_list

    if @co_index <= list.size
      id = list[@co_index - 1][:id]
    end