__gnu_pbds::detail::pat_trie_map(3cxx) on Linux
The text 73ac96cd68d9, as Debian 10 (Buster) shipped it.
PATRICIA trie. This implementation loosely borrows ideas from: 1) Fast Mergeable Integer Maps, Okasaki, Gill 1998 2) Ptset: Sets of integers implemented as Patricia trees, Jean-Christophe Filliatr, 2000.