take(1) can be dangerous

When putting together reactive networks using Reactive Extensions (e.g. RxJS in Javascript / Typescript), I often need logic that responds to a single event. `take(1)` is useful in this situation.

However, more than once, `take(1)` is a cursed operator, because it can easily cause an RxNetwork *to go dead*. This is because after a single event it completes.

It’d behoove one to remember this and make sure that’s really what you want. In this case, I was doing a `filter()` after a `take(1)` and it resulted in a reactive stream that send no events and just completed. I really needed to put the `filter` first.