code: def print_usage(self):
          
          print 'Total Usage: %f compute seconds' % self.box_usage
          cost = self.box_usage * 0.14
          print 'Approximate Cost: $%f' % cost
docs: Print the BoxUsage and approximate costs of all requests made on
          this specific SDBConnection instance.
          
          .. tip:: This can be out of date, and should only be treated as a
              rough estimate. Also note that this estimate only applies to the
              requests made on this specific connection instance. It is by
              no means an account-wide estimate.