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: report.rb
    path of file: ./repos/knapsack/lib/knapsack
    
    the code of the file until where you have to start completion: module Knapsack
  class Report
    include Singleto
    
    def open
      report = File.read(report_path)
      JSON.parse(report)
    rescue Errno::ENOENT
      raise "Knapsack report file #{report_path} doesn't exist. Please generate report first!"
    end

    private

    def report_json
      Presenter.report_json
    end
  end