Function block_on_stream 

pub fn block_on_stream<'a, F, S, R>(f: F) -> SingleThreadIterator<'a, R> 
where
    F: FnOnce(Handle) -> S,
    S: Stream<Item = R> + Send + Unpin + 'a,
    R: Send + 'a,

Returns an iterator wrapper around a stream, blocking the current thread for each item.