from sage.sets.finite_enumerated_set import FiniteEnumeratedSet
from sage.categories.sets_cat import cartesian_product
I = FiniteEnumeratedSet(range(n))
J = FiniteEnumeratedSet(range(n))
from sage.sets.finite_enumerated_set import FiniteEnumeratedSet
from sage.categories.sets_cat import cartesian_product
I = FiniteEnumeratedSet(range(n))
J = FiniteEnumeratedSet(range(n))