# File lib/test/unit/data-sets.rb, line 25
      def keep
        new_data_sets = self.class.new
        all_data_sets = Enumerator.new do |yielder|
          block = lambda do |(data_set, options)|
            yielder << [data_set, options]
          end
          @procs.each(&block)
          @variables.each(&block)
          @value_sets.each(&block)
        end
        all_data_sets.each do |data_set, options|
          next if options.nil?
          next unless options[:keep]
          new_data_sets.add(data_set, options)
        end
        new_data_sets
      end