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: pebble.rb
    path of file: ./repos/jekyll-import/lib/jekyll-import/importers
    
    the code of the file until where you have to start completion: module JekyllImport
  module Importers
    class Pebble < Importer
      def self.require_deps
        JekyllImport.require_with_fallback(%w(
          nokogiri
          safe_yaml
        ))
      end

      def self.specify_options(c) 
        c.option "directory", "--directory PATH", "Pebble source directory"
   
    
      def self.traverse_posts_within(directory, &block) 
        Dir.foreach(directory) do |fd|
          path = File.join(directory, fd)
          if fd == '.' || fd == '..'
            next
          elsif File.directory?(path) 
            traverse_posts_within(path, &block)
          elsif path.end_with?('xml')
            yield(path) if block_given?
          else
          end
        end