Reduces a Result<Result<T, E>, E> to a Result<T, E>. If the outer result is Err, the outer Err will be returned. If the outer result is Ok, the inner result will be returned.
Reduces a Result<Result<T, E>, E> to a Result<T, E>. If the outer result is Err, the outer Err will be returned. If the outer result is Ok, the inner result will be returned.