code: public static Observable<RxComapiClient> initialiseShared(@NonNull Application app, @NonNull ComapiConfig config) {
          String error = checkIfCanInitialise(app, config, true);
          if (error != null) {
              return Observable.error(new Exception(error));
          }
  
          RxComapiClient client = createShared(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.