How to use the apollo-link-batch.BatchLink function in apollo-link-batch

})
				)
					.then((results: FetchResult[]) => {
						(emittedResponse = true) && notifier.emit('res', results);
						// we have data and can send it to back up the link chain
						observer.next(results);
						observer.complete();
						return results;
					})
					.catch(err => {
						emittedResponse || notifier.emit('res', err);
						observer.error(err);
					});
			});

		this.batcher = new BatchLink({
			batchInterval: options.batchInterval,
			batchHandler
		});
	}

batchKey ||
      ((operation: Operation) => {
        const context = operation.getContext();

        const contextConfig = {
          http: context.http,
          options: context.fetchOptions,
          credentials: context.credentials,
          headers: context.headers,
        };

        //may throw error if config not serializable
        return selectURI(operation, uri) + JSON.stringify(contextConfig);
      });

    this.batcher = new BatchLink({
      batchInterval: this.batchInterval,
      batchMax: this.batchMax,
      batchKey,
      batchHandler,
    });
  }

return () => {
          if (!sub.closed) {
            sub.unsubscribe();
          }
        };
      });
    };

    const batchKey =
      options.batchKey ||
      ((operation: Operation) => {
        return this.createBatchKey(operation);
      });

    this.batcher = new BatchLink({
      batchInterval: this.batchInterval,
      batchMax: this.batchMax,
      batchKey,
      batchHandler,
    });
  }

id: queryMap[queryKey],
        };
      });

      apolloFetch(printedOperations)
        .then((data) => {
          observer.next(data);
          observer.complete();
        })
        .catch(observer.error.bind(observer));
    });
  };

  const apolloLink = new BatchHttpLink();
  return Object.assign(apolloLink, {
    batcher: new BatchLink({
      batchInterval: apolloLink.batchInterval,
      batchMax: apolloLink.batchMax,
      batchHandler: batchHandler.bind(apolloLink),
    }),
  });
};