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: user_informer.rb
    path of file: ./repos/honeybadger-ruby/lib/honeybadger/rack
    
    the code of the file until where you have to start completion: require 'forwardable'

module Honeybadger
  module Rack
    # Middleware for Rack applications. Adds an error ID to the Rack response
    # when an error has occurred.
    class UserInformer
      ext
    
      def call(env)
        return @app.call(env) unless config[:'user_informer.enabled']
        status, headers, body = @app.call(env)
        if env['honeybadger.error_id']
          new_body = []
          replace  = replacement(env['honeybadger.error_id'])
          body.each do |chunk|
            new_body << chunk.gsub("<!-- HONEYBADGER ERROR -->", replace)
          end
          body.close if body.respond_to?(:close)
          headers['Content-Length'] = new_body.reduce(0) { |a,e| a += e.bytesize }.to_s
          body = new_body
        end