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: base_config.rb
    path of file: ./repos/gitlabhq/app/models/bulk_imports/file_transfer
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module BulkImports
  module FileTransfer
    class BaseConfig
      include Gitlab::Utils::StrongMemoize

      UPLOADS_RELATI
    
      def export_service_for(relation)
        if tree_relation?(relation)
          ::BulkImports::TreeExportService
        elsif file_relation?(relation)
          ::BulkImports::FileExportService
        else
          raise ::BulkImports::Error, 'Unsupported export relation'
        end