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: tmpio.rb
    path of file: ./repos/passenger/src/ruby_supportlib/phusion_passenger/utils
    
    the code of the file until where you have to start completion: require 'tmpdir'
require 'fileutils'

module Phus
    
def self.mktmpdir(prefix_suffix=nil, tmpdir=nil)
  case prefix_suffix
  when nil
    prefix = "d"
    suffix = ""
  when String
    prefix = prefix_suffix
    suffix = ""
  when Array
    prefix = prefix_suffix[0]
    suffix = prefix_suffix[1]
  else
    raise ArgumentError, "unexpected prefix_suffix: #{prefix_suffix.inspect}"
  end