`Length()` Function for Collection Types

[zliang-akamai]

It's nice to have Length function for collection types (set, list, map, etc.), so we won't have to do len(list.Elements()) which is wasting time to allocate and release memory because Elements() make a new slice internally.

If you are willing to add this feature, I can try to put up a PR to implement it. Let me know.

[bbasata]

It's nice to have Length function for collection types (set, list, map, etc.), so we won't have to do len(list.Elements()) which is wasting time to allocate and release memory because Elements() make a new slice internally.

If you are willing to add this feature, I can try to put up a PR to implement it. Let me know.

@zliang-akamai: a PR would be welcomed.