sagemathgh-38602: Allow for python sets to be counted as sets

    
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Fixes Issue sagemath#32265


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URL: sagemath#38602
Reported by: Aram Dermenjian
Reviewer(s): Travis Scrimshaw

src/sage/combinat/subset.py

@@ -321,8 +321,10 @@ def __contains__(self, value):
             True
             sage: 2 in S
             False
+            sage: {1, 2} in S
+            True
         """
-        if value not in Sets():
+        if value not in Sets() and not isinstance(value, (set, frozenset)):
             return False
         return all(v in self._s for v in value)