Github user sihuazhou commented on the issue:
https://github.com/apache/flink/pull/5749
Hi, @StefanRRichter That's a good question, I think the `Collection` looks
better then `Iterable`... the benefit is that the api looks more consistency
with the java api, and maybe convenient to users in some scenario. (e.g. when
they want to add a `Set` of elements, they don't need to convert it to a `List`
anymore)---
