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: pstore.rb
    path of file: ./repos/powerstation/powerstation/lib/compiled-jruby/lib/ruby/stdlib/cgi/session
    
    the code of the file until where you have to start completion: #
# cgi/session/pstore.rb - persistent storage of marshalled session data
#
# Documentation: William Webber (william@williamwebber.com)
#
# == Overview
#
# This file provides the CGI::Session::PStore class, which builds
# persistent of session data on top of the pstore library.  See
# cgi
    
      def initialize(session, option={})
        dir = option['tmpdir'] || Dir::tmpdir
        prefix = option['prefix'] || ''
        id = session.session_id
        require 'digest/md5'
        md5 = Digest::MD5.hexdigest(id)[0,16]
        path = dir+"/"+prefix+md5
        path.untaint
        if File::exist?(path)
          @hash = nil
        else
          unless session.new_session
            raise CGI::Session::NoSession, "uninitialized session"
          end