What is about the function above?

Bindings doesn't support overloads properly. Sometimes new names for overloads wrapping are required.

I think only one overload should be in python in nearest future

GAPI_EXPORTS_W_SIMPLE is for simple key/value maps only (CV_PROP/CV_PROP_RW only).

It passes/handles arguments "by value".

Normal EXPORTS_W uses smart pointers for that and handles arguments "by reference". It should be used by default for classes.

IMHO, It is misused almost everywhere in gapi module.

@TolyaTalamanov ☝️

I see, but if this object is returned from function which also wrapped, it should be SIMPLE
Net - https://github.com/opencv/opencv/blob/master/modules/dnn/include/opencv2/dnn/dnn.hpp#L390
function https://github.com/opencv/opencv/blob/master/modules/dnn/include/opencv2/dnn/dnn.hpp#L759

Because for CV_EXPORTS_W wrapper generates code for Ptr<Object> but function return Object by value, so it means in case Object is returned from function need to use CV_EXPORTS_W_SIMPLE, doesn't it ?

It's a reason why in G-API uses GAPI_EXPORTS_W_SIMPLE almost for all classes

So you are right, need to avoid it for objects which is not pimpl, but in case GCompiledStreaming it works fine. Opened a ticket