Function flattened 

pub fn flattened<S>(s: S) -> FlattenedStream<S>

Wrap a TryStream<T> whos items, TryStream::::Ok, implement Paged. functionally, this means a struct wrapping a Vec will return the inner Vec instead of the struct

in other words, a Stream of the form Stream<Item = Foo> will instead be Stream<Item = Vec<Boo>>

    struct Foo {
        items: Vec<Boo>
    }

    impl Paged for Foo {
        type Message = Boo;
        fn messages(self) -> Vec<Boo> {
            self.items
        }
        /* .. */
    }