code: public static Observable<RxComapiClient> initialise(@NonNull Application app, @NonNull ComapiConfig config) {
  
          String error = checkIfCanInitialise(app, config, false);
          if (!TextUtils.isEmpty(error)) {
              return Observable.error(new Exception(error));
          }
  
          RxComapiClient client = new RxComapiClient(config);
          return client.initialise(app, config.getCallbackAdapter() != null ? config.getCallbackAdapter() : new CallbackAdapter(), client);
      }
docs: Build SDK client. Can be called only once in onCreate callback on Application class.