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: biff8.rb
    path of file: ./repos/spreadsheet/lib/spreadsheet/excel/writer
    
    the code of the file until where you have to start completion: require 'spreadsheet/encodings'

module Spreadsheet
  module Excel
    module Writer
##
# This Module collects writer methods such as unicode_string that are specific
# to Biff8. This Module is likely to be expanded as Support for older Versions
# of Excel grows and methods get moved here for disambiguation.
module Biff8
  include Spreadsheet::Encodings
  ##
  # Check whether the string _data_ can be compressed (i.e. every second byte
  # is a Null-byte) and perform compression.
  # Returns the data and compression_status (0/1)
  def compress_unicode_string data
    compressed = internal('')
    expect_null = false
    data.each_byte do |byte|
      if expect_null
        if byte != 0
          return [data, 1] # 1 => Data consists of wide Chars
        end
        expect_null = false
      else
        compressed << byte
        expect_null = true
      end
    end
    [compressed, 0] # 0 => Data consists of compressed Chars
  end
  ##
  # Encode _string_ into a Biff8 Unicode String. Header and body are encoded
  # separately by #_unicode_string. This method simply combines the two.
  def unicode_string string, count_length=1
    header, data, _ = _unicode_string string, count_length
    header << data
  end
  @@
    
  def _unicode_string string, count_length=1
    data = internal string
    size = data.send(@@bytesize) / 2
    fmt = count_length == 1 ? 'C2' : 'vC'
    data, wide = compress_unicode_string data
    opts = wide
    header = [
      size, # Length of the string (character count, ln)
      opts, # Option flags:
            # Bit  Mask  Contents
            #   0  0x01  Character compression (ccompr):
            #            0 = Compressed (8-bit characters)
            #            1 = Uncompressed (16-bit characters)
            #   2  0x04  Asian phonetic settings (phonetic):
            #            0 = Does not contain Asian phonetic settings
            #            1 = Contains Asian phonetic settings
            #   3  0x08  Rich-Text settings (richtext):
            #            0 = Does not contain Rich-Text settings
            #            1 = Contains Rich-Text settings
      #0x00,# (optional, only if richtext=1) Number of Rich-Text
            #                                formatting runs (rt)
      #0x00,# (optional, only if phonetic=1) Size of Asian phonetic
            #                                settings block (in bytes, sz)
    ].pack fmt
    data << '' # (optional, only if richtext=1)
               # List of rt formatting runs (➜ 3.2)
    data << '' # (optional, only if phonetic=1)
               # Asian Phonetic Settings Block (➜ 3.4.2)
    [header, data, wide]
  end