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: mapping.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/devise-4.3.0/lib/devise
    
    the code of the file until where you have to start completion: module Devise
  # Responsible for handling devise mappings and routes configuration. Each
  # resource configured by devise_for in routes is actually creating a mapping
  # object. You can refer to devise_for i
    
    def default_used_route(options)
      singularizer = lambda { |s| s.to_s.singularize.to_sym }

      if options.has_key?(:only)
        @used_routes = self.routes & Array(options[:only]).map(&singularizer)
      elsif options[:skip] == :all
        @used_routes = []
      else
        @used_routes = self.routes - Array(options[:skip]).map(&singularizer)
      end