code: public BulkUpdateRequestBuilder upsert() {
          return new BulkUpdateRequestBuilder(bulkWriteOperation, query, true, codec, replacementCodec, collation, null);
      }
docs: Specifies that the request being built should be an upsert.
  
  @return a new builder that allows only update and replace, since upsert does not apply to remove.
  @mongodb.driver.manual tutorial/modify-documents/#upsert-option Upsert