Multiple Issues with modify action for SAP SF OData API

I am using this library for developing a Python application that uses SAP SuccessFactors OData API. I spent last few days to resolve following issues with performing modify/update action but without any success. I finally came here to seek your help and suggestion. Please note that my application is already using this library for several OData query operations but I would prefer to use it also for update, create and delete operations too.

• Single update request using "PUT" method is making the desired update into HttpError because the status code returned is 200 instead of 204. This is because the update_entity() function in the class EntitySetProxy expects it to be 204 always.

• SAP SuccessFactors expects a custom method called "UPSERT" but the EntityModifyRequest class identifies it as invalid method.

• Batch update request even with only one update changeset is failing with the "BadRequestException" (400) error : "Missing boundary delimiter at line '4'.". Code wise all looks good and as suggested in the usage guide. Also, the header as well as the body (prints as below in [] parentheses) of the batch request looks fine too. Could it be because of 2 line breaks on line 4 of the body?

Batch Req. Header: [{'Content-Type': 'multipart/mixed;boundary=batch_1850_4989_2562'}]
Batch Req. Body: [
--batch_1850_4989_2562
Content-Type: multipart/mixed;boundary=changeset_2364_6806_2818

--changeset_2364_6806_2818
Content-Type: application/http
Content-Transfer-Encoding:binary

PUT PickListValueV2(PickListV2_effectiveStartDate=datetime'2020-10-23T00:00:00',PickListV2_id='employeeGroup',externalCode='EX') HTTP/1.1
Accept: application/json
Content-Type: application/json

{"label_en_DEBUG": "External Employee", "status": "A"}
--changeset_2364_6806_2818--
--batch_1850_4989_2562--]
Sample Code:

Start with EntitySetProxy.update_entity() and EntityModifyRequest, then reproduce the PUT, UPSERT, and batch update examples from the issue and usage guide. Check the generated batch body and response handling; done means 200 updates are accepted, UPSERT is recognized, and the single-change-set batch request is accepted without the boundary error.