code: public Collection<PartnerSubscription> list(long partnerId, long accountId)
      {
          return HTTP.GET(String.format("/v2/partners/%d/accounts/%d/subscriptions", partnerId, accountId), PARTNER_SUBSCRIPTIONS).get();
      }
docs: Returns the set of subscriptions.
  @param partnerId The id of the partner for the subscriptions
  @param accountId The id of the account for the subscriptions
  @return The set of subscriptions