code: public UsageRecordSummaryCollection usageRecordSummaries(
        Map<String, Object> params, RequestOptions options) throws StripeException {
      String url =
          String.format(
              "%s%s",
              Stripe.getApiBase(),
              String.format(
                  "/v1/subscription_items/%s/usage_record_summaries",
                  ApiResource.urlEncodeId(this.getId())));
      return requestCollection(url, params, UsageRecordSummaryCollection.class, options);
    }
docs: For the specified subscription item, returns a list of summary objects. Each object in the list
  provides usage information that’s been summarized from multiple usage records and over a
  subscription billing period (e.g., 15 usage records in the billing plan’s month of September).
  
  <p>The list is sorted in reverse-chronological order (newest first). The first list item
  represents the most current usage period that hasn’t ended yet. Since new usage records can
  still be added, the returned summary information for the subscription item’s ID should be seen
  as unstable until the subscription billing period ends.