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: phone_data_importer.rb
    path of file: ./repos/telephone_number/lib/importers
    
    the code of the file until where you have to start completion: module TelephoneNumber
  require 'nokogiri'
  class PhoneDataImporter
    attr_reader :data, :file, :override

    def initialize(file_name, override: false)
      @data = {}
      @file = File.open(file_name) { |f| Nokogiri::XML(f) }
      @override = overrid
    
    def underscore(camel_cased_word)
      return camel_cased_word unless camel_cased_word.match?(/[A-Z-]|::/)
      word = camel_cased_word.to_s.gsub(/::/, '/')
      word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2')
      word.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
      word.tr!('-', '_')
      word.downcase!
      word
    end