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: util.rb
    path of file: ./repos/kontena/cli/lib/kontena
    
    the code of the file until where you have to start completion: module Kontena
  module Util
    def self.included(base)
      base.extend(ClassMethods)
    end

    def symbolize_keys(obj)
      cas
    
    def stringify_keys!(obj)
      case obj
      when Hash
        obj.keys.each { |k| obj[k.to_s] = stringify_keys!(obj.delete(k)) }
      when Array
        obj.map! { |v| stringify_keys!(v) }
      else
      end