fn err_into<E>(self) -> ErrInto<Self, E>
    where
        Self: Sized,
        Self::Error: Into<E>,
    {
        assert_stream::<Result<Self::Ok, E>, _>(ErrInto::new(self))
    }
Wraps the current stream in a new stream which converts the error type
into the one provided.

# Examples

```
# futures::executor::block_on(async {
use futures::stream::{self, TryStreamExt};

let mut stream =
stream::iter(vec![Ok(()), Err(5i32)])
.err_into::<i64>();

assert_eq!(stream.try_next().await, Ok(Some(())));
assert_eq!(stream.try_next().await, Err(5i64));
# })
```
futures-util/src/stream/try_stream/mod.rs