Schema for "config" parameter for plugins

So. I making openapi specs for Admin API (just for codegen actually), and i really don’t understand, what is the format for describing plugin configs in the “config” parameter? Okay, we have a type, the default value, a checkmark which explains is this parameter mandatory or not, but how is it working inside? This is not a jsonschema file format, but obviously something else, and I really need to understand how this format works. Can someone tell me, or give a link to the source code of the Kong where this format is described? thanks!