def ok_with(combination)
      @ok_experiments << combination
      return unless combination.is_a?(Array)

      combination.each do |element|
        @ok_experiments.delete(element)
      end
    end
def ok_with(combination)
      @ok_experiments << combination
      return unless combination.is_a?(Array)

      combination.each do |element|
        @ok_experiments.delete(element)
      end
    end
Keep track of ok experiments depending on the current combination.
 It keep the combinations unique removing single replacements after the
 first round.
 @return void