Fix import: move permutations to top-level

compact_sets.py

@@ -13,7 +13,7 @@ Mathematical foundations:
 
 from __future__ import annotations
 from fractions import Fraction
-from itertools import combinations, permutations
+from itertools import combinations, permutations, permutations
 from math import prod, log
 from operator import add
 from random import choice, choices, seed
@@ -624,8 +624,6 @@ class HarmonicSpace:
             valid_pairings.append(pairings)
 
         # Generate all permutations and filter valid ones
-        from itertools import permutations
-
         all_maps = []
         num_changing = len(c2_changing)