code: public static Batch removeShipments(String id, String[] shipmentIds)
  			throws AuthenticationException, InvalidRequestException, APIConnectionException, APIException {
  		Map<String, Object> params = new HashMap<String, Object>();
  		params.put("__list", shipmentIds);
  		return request(RequestMethod.POST, instanceURL(Batch.class, id) + "/remove_shipments", params, Batch.class,
  				null);
  	}
docs: Remove shipments to an existing batch provided by id. This method
  corresponds to https://api.goshippo.com/batches/<i>BATCH OBJECT ID</i>/remove_shipments
  endpoint defined in https://goshippo.com/docs/reference#batches-remove-shipments
  
  @param id
  Batch object ID
  @param shipmentIds
  Array of shipment Ids to be removed from the batch
  @return The Batch object after shipments have been removed