What is intention/pattern for multi-typed $X$ inputs for kernels and everything else?

[cottrell]

I have yet to find an example for this.

It looks like there is an assumption that x1, x2 are tensors. Perhaps some parts of the framework support x1 being a list of tensors? Or a dict? It's not obvious as I'm trying things. The obvious example is int and float features which flow into different sub kernels.