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: qiniu.rb
    path of file: ./repos/backup/lib/backup/storage
    
    the code of the file until where you have to start completion: require "qiniu"

module Backup
  module Storage
    class Qiniu < Base
      includ
    
      def check_configuration
        required = %w[access_key secret_key bucket]

        raise Error, <<-EOS if required.map { |name| send(name) }.any?(&:nil?)
          Configuration Error
          #{required.map { |name| "##{name}" }.join(", ")} are all required
        EOS
      end