code: @Override
      public InstagramSingleObjectResponse createUserSubscription(String clientId,
                                                                  String clientSecret,
                                                                  String callbackUrl) throws InstagramError {
          return instagramRealtime.createUserSubscription(clientId, clientSecret, callbackUrl,
                                                          InstagramSubscriptionObjectTypes.USER.getObject(), SUBSCRIPTION_ASPECT);
      }
docs: /* REAL-TIME SUBSCRIPTIONS