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

require 'bb/client'

##
# Models logic pertaining to the verification and logging of MHV accounts
#
# @param user [User] the user object
#
class MHVAccountTypeService
  ELIGIBLE_D
    
  def fetch_eligible_data_classes
    if cached_eligible_data_class
      json = Oj.load(cached_eligible_data_class)
      Common::Collection.new(::EligibleDataClass, **json.symbolize_keys).members.map(&:name)
    else
      bb_client = BB::Client.new(session: { user_id: @user.mhv_correlation_id })
      bb_client.authenticate
      bb_client.get_eligible_data_classes.members.map(&:name)
    end