This change is a major renaming of the base class in Immutable.js from Iterable to Collection. In doing so the existing Collection subclass is completely removed from the hierarchy.

In my experience the difference between the two has been a constant point of confusion for newcomers to the library, and with ES2015 becoming a standard part of the development environment, the name Iterable has become ambiguous at best and required awkward workarounds in type definitions before this change.

To ease conversion, the Collection class is still also exported as Iterable and the new isCollection function is aliased as isIterable - existing code will not break.