Idiomatic Rust uses lowercase for acronyms for all characters after the first e.g. `std::net::TcpStream`. PSBT (Partially Signed Bitcoin Transaction) should be rendered `Psbt` in Rust code if we want to write idiomatic Rust. Use `Psbt` instead of `PSBT` when aliasing the import of `PartiallySignedTransaction` from `bitcoin` library.