# File lib/rhc/rest/cartridge.rb, line 74
      def usage_rates
        rate = attribute(:usage_rate_usd).to_f rescue 0.0
        if rate > 0
          {rate => []}
        elsif attribute(:usage_rates).present?
          attribute(:usage_rates).inject({}) do |plans_by_rate, rate|
            if (usd = rate['usd'].to_f rescue 0.0) > 0
              (plans_by_rate[usd] ||= []) << rate['plan_id']
            end
            plans_by_rate
          end
        end
      end