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

require 'json_marshal/marshaller'
require 'common/exceptions'

module AppealsApi
  cl
    
    def assign_veteran_icn
      # Ensure veteran_icn is set - this value will be retained after the PII is deleted
      if veteran_icn.blank?
        self.veteran_icn = if (header_icn = auth_headers['X-VA-ICN'].presence)
                             # Decision Reviews API
                             header_icn
                           else
                             # Notice of Disagreements API v0
                             form_data.dig('data', 'attributes', 'veteran', 'icn').presence
                           end