How do I tell IL2CPP to generate code for a generic method?

I have a generic method like

void MyMethod<T>() { ... }

and when compiling with IL2CPP the method is missing for some value types I'm using.

The method is private and defined in another separate library.

A link.xml file won't help here, as the problem comes from the method being generic.
IL2CPP can't generate an implementation because T is not known yet.

I vaguely remember there being a way to instruct IL2CPP to generate generic implementations/instantiations of methods/code by using some attribute.

[assembly: IL2CPPGenericMethod("SomeLibrary.MyMethod", typeof(SomeStructType))]

Being able to somehow specify types and generic parameters for it would solve this.
How can I do this?