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: caseflow_request.rb
    path of file: ./repos/vets-api/modules/appeals_api/app/controllers/concerns/appeals_api
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module AppealsApi
  module CaseflowRequest
    extend ActiveSupport::Concern

    # Redefine this in the 
    
    def icn_to_ssn!(icn)
      res = MPI::Service.new.find_profile_by_identifier(identifier: icn, identifier_type: MPI::Constants::ICN)
      raise_unusable_response('MPI') if res.status == :server_error

      ssn = res.profile&.ssn
      raise_veteran_not_found if ssn.blank?

      ssn
    end