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: po.rb
    path of file: ./repos/truffleruby/lib/mri/rdoc/generator/pot
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
##
# Generates a PO format text

class RDoc::Generator::POT::PO

  ##
  # Creates an object that represents PO format.

  def initialize
    @entries = {}
    add_header
  end

  ##
  # Adds a PO entry to the PO.

  def add entry
    existing_entry = @entries[entry.msgid]
    if existing_entr
    
  def header_entry
    comment = <<-COMMENT
SOME DESCRIPTIVE TITLE.
Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
This file is distributed under the same license as the PACKAGE package.
FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
    COMMENT

    content = <<-CONTENT
Project-Id-Version: PACKAGE VERSEION
Report-Msgid-Bugs-To:
PO-Revision-Date: YEAR-MO_DA HO:MI+ZONE
Last-Translator: FULL NAME <EMAIL@ADDRESS>
Language-Team: LANGUAGE <LL@li.org>
Language:
MIME-Version: 1.0
Content-Type: text/plain; charset=CHARSET
Content-Transfer-Encoding: 8bit
Plural-Forms: nplurals=INTEGER; plural=EXPRESSION;
    CONTENT

    options = {
      :msgstr => content,
      :translator_comment => comment,
      :flags => ['fuzzy'],
    }
    RDoc::Generator::POT::POEntry.new('', options)
  end