fn sink_err_into<E>(self) -> err_into::SinkErrInto<Self, Item, E>
    where
        Self: Sized,
        Self::Error: Into<E>,
    {
        assert_sink::<Item, E, _>(SinkErrInto::new(self))
    }
Map this sink's error to a different error type using the `Into` trait.

If wanting to map errors of a `Sink + Stream`, use `.sink_err_into().err_into()`.
futures-util/src/sink/mod.rs