Set Intersection is Self-Distributive/General Result

Theorem
Let $\family {\mathbb S_i} _{i \mathop \in I}$ be an $I$-indexed family of sets of sets.

Then:
 * $\ds \bigcap_{i \mathop \in I} \bigcap \mathbb S_i = \bigcap \bigcap_{i \mathop \in I} \mathbb S_i$