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: accession_deaccessions_subreport.rb
    path of file: ./repos/archivesspace/reports/accessions/accession_deaccessions_subreport
    
    the code of the file until where you have to start completion: class AccessionDeaccessionsSubreport < AbstractSubreport
  attr_accessor :total_extent

  def initialize(parent_report, accession_id)
    super(parent_repo
    
  def query_string
    "select
      description,
      notification as notification_sent,
      group_concat(distinct date.begin SEPARATOR ', ') as date,
      sum(extent.number) as extent_number,
      GROUP_CONCAT(distinct extent.extent_type_id SEPARATOR ', ') as extent_type
    from deaccession
      left outer join date on date.deaccession_id = deaccession.id
      left outer join extent on extent.deaccession_id = deaccession.id
    where deaccession.accession_id = #{db.literal(@accession_id)}
    group by deaccession.id"
  end