pub fn get_all_bin<K>(&self, key: K) -> GetAll<'_, Binary>
    where
        K: AsMetadataKey<Binary>,
    {
        GetAll {
            inner: key.get_all(self),
            phantom: PhantomData,
        }
    }
Like get_all, but for Binary keys (for example "trace-proto-bin").

# Examples

```
# use tonic::metadata::*;
let mut map = MetadataMap::new();

map.insert_bin("trace-proto-bin", MetadataValue::from_bytes(b"hello"));
map.append_bin("trace-proto-bin", MetadataValue::from_bytes(b"goodbye"));

{
let view = map.get_all_bin("trace-proto-bin");

let mut iter = view.iter();
assert_eq!(&"hello", iter.next().unwrap());
assert_eq!(&"goodbye", iter.next().unwrap());
assert!(iter.next().is_none());
}

// Attempting to read a key of the wrong type fails by not
// finding anything.
map.append("host", "world".parse().unwrap());
assert!(map.get_all_bin("host").iter().next().is_none());
assert!(map.get_all_bin("host".to_string()).iter().next().is_none());
assert!(map.get_all_bin(&("host".to_string())).iter().next().is_none());

// Attempting to read an invalid key string fails by not
// finding anything.
assert!(map.get_all_bin("host{}-bin").iter().next().is_none());
assert!(map.get_all_bin("host{}-bin".to_string()).iter().next().is_none());
assert!(map.get_all_bin(&("host{}-bin".to_string())).iter().next().is_none());
```
tonic/src/metadata/map.rs