# File lib/faster_csv.rb, line 1104
    def self.instance(data = $stdout, options = Hash.new)
      # create a _signature_ for this method call, data object and options
      sig = [data.object_id] +
            options.values_at(*DEFAULT_OPTIONS.keys.sort_by { |sym| sym.to_s })

      # fetch or create the instance for this signature
      @@instances ||= Hash.new
      instance    =   (@@instances[sig] ||= new(data, options))

      if block_given?
        yield instance  # run block, if given, returning result
      else
        instance        # or return the instance
      end
    end