Macro ocaml::import

macro_rules! import {
    ($vis:vis fn $name:ident($($arg:ident: $t:ty),*) $(-> $r:ty)?) => { ... };
    ($($vis:vis fn $name:ident($($arg:ident: $t:ty),*) $(-> $r:ty)?;)+) => { ... };
}

Import OCaml functions