src/sage/sets/cartesian_product.py: Make MRO consistent

Author: Matthias Koeppe

src/sage/sets/cartesian_product.py

@@ -404,7 +404,10 @@ def __hash__(self):
         return hash(self.cartesian_factors())
 
 
-class CartesianProduct_unique(CartesianProduct_with_element_wrapper, UniqueRepresentation):
+class CartesianProduct_unique(UniqueRepresentation, CartesianProduct_with_element_wrapper):
+    r"""
+    A Cartesian product with :class:`~sage.structure.unique_representation.UniqueRepresentation` behavior.
+    """
     pass