We might have a terminology issue here, since according to Wikipedia
there is some dispute over whether or not to include the equality case
For what it is worth, I'm in the school that subset implies proper subset
Wikipedia's pedantry notwithstanding, I don't think this is a useful position *when talking about Python sets*, since Python's set's .issubset() method returns True when the argument is the same set:
Or did I miss a wink?