I've made an attempt at patching set_issubset() to match the Python from Raymond's message. I've rearranged the set_issubset function so that it checks for a set/frozenset, dict, or iterable in that order. In the iterable case it will create a temporary set and add elements to it as it consumes them from the iterable, returning early when possible.

This is my first patch, please let me know how I may improve it!