Macro import_interface

macro_rules! import_interface {
    (
        $sig: expr;
        $name: ident;
        $(implements $($parent_interface: ty),+;)?
        $(
            $(#[doc=$doc:expr])*
            fn $method:ident (&self $(, $arg:ident : $arg_ty:ty)*) -> $ret:ty;
        )*
    ) => { ... };
}