fn map_ok<T, F>(self, f: F) -> MapOk<Self, F>
    where
        Self: Sized,
        F: FnMut(Self::Ok) -> T,
    {
        assert_stream::<Result<T, Self::Error>, _>(MapOk::new(self, f))
    }
Wraps the current stream in a new stream which maps the success value
using the provided closure.

# Examples

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

let mut stream =
stream::iter(vec![Ok(5), Err(0)])
.map_ok(|x| x + 2);

assert_eq!(stream.try_next().await, Ok(Some(7)));
assert_eq!(stream.try_next().await, Err(0));
# })
```
futures-util/src/stream/try_stream/mod.rs