Question: missing capture socket in zmq_proxy (Proxy class) and how to use a capture socket in a Proxy

[pmbanugo]

I'm going through pub-sub tracing (espresso pattern) in the book and I couldn't get the sample code working. Reading through the zmq_proxy I see that the Proxy type in typescript doesn't support passing the third socket (i.e. the capture socket).

Is there a reason why that's missing? How can I achieve similar thing from the book with a capture socket using the current features?