fixed ucombo hash

sorted returns a (unhashable)  list, so much convert this list to a tuple before hashing.

uncertainties/ucombo.py

@@ -126,7 +126,7 @@ def __str__(self: UCombo) -> str:
     def __hash__(self: UCombo) -> int:
         if self._hash is None:
             self._hash = hash(
-                sorted(tuple((key, value) for key, value in self.expanded.items()))
+                tuple(sorted((key, value) for key, value in self.expanded.items()))
             )
         return self._hash