About holepunching test

I'm interested in the holepunching test (torrent/ut-holepunching_test.go).

In the test, Seeder and Leecher-Leecher realized the hole punching function with the help of Leecher. I would like to ask if I need to configure the role of Leecher in the actual use scenario?

I want to realize a scenario: start two nodes (client) behind different NAT devices respectively, and then the two nodes realize connecting directly. How to use the interface provided in anacrolix/torrent to realize it? (Looks like anacrolix/torrent doesn't expose an explicit interface to provide direct connection functionality)