REST API - how to create multiple records in one payload?

Summary:

I tried to use REST API to create multiple learning content in one Payload, I did exactly the same as Oracle support document 2644754.1 or 2746047.1, but I got the error "400 Bad Request", "part1 failed: null".

I have hundreds learning contents need to create in Fusion, HDL doesn't support, we can only do it used REST API.

Have anyone successfully created multiple items in one Payload? Would you pls help me? Thank you!

Content (required):

Used REST API, I created the learning content one by one successfully.

POST https://fa-epuh-test-saasfaprod1.fa.ocs.oraclecloud.com/hcmRestApi/resources/latest/learningContentItems

Content-Type: application/json