Unions of subsets of a fixed open set X are not known to be subsets of X #30401
Description
See the following:
sage: T = Manifold(2, 'T', start_index=1)
sage: U0 = T.open_subset("U0", latex_name="U_0")
sage: Uh = T.open_subset("Uh", latex_name="U_h")
sage: T.declare_union(U0, Uh)
sage: I0h = U0.intersection(Uh, name="I0h", latex_name="I_{0h}")
sage: X1 = I0h.open_subset('X1', "X_1")
sage: X2 = I0h.open_subset('X2', "X_2")
sage: X3 = I0h.open_subset('X3', "X_3")
sage: X1.union(X2).is_subset(I0h)
False
This means I cannot declare I0h as the union of 3 subsets.
Component: manifolds
Author: Eric Gourgoulhon
Branch/Commit: bbe5d11
Reviewer: Travis Scrimshaw
Issue created by migration from https://trac.sagemath.org/ticket/30401