Preparation Tool in Fine-Tuning while coding in C#

I see based on OpenAI documentation that only “Create fine-tune” API exists, but there is no API to “Prepare training data” as discussed here.
It talks about CLI preparation tool, but it is not available as API. So, what is the expectation? Calling Python from C# ?

The expectation is that you, the developer, create and validate your own JSONL training data file.

Having the same or related problem. I’m trying to use the openai tools,prepare_data and openai api in a Windows command prompt window using python 3.8. I have a .jsonl file already prepared but would like to check it, or try to create a fine tuning job. Neither invocation does anything but wait a few seconds then return with no message of any kind. My api key is in the environment variable OPENAI_API_KEY.

What am I doing wrong?