===== Cover =====
==== Set ====
| @#55CCEE: context     | @#55CCEE: $X$ |
| @#FFBB00: definiendum | @#FFBB00: $C$ in it |
| @#55EE55: postulate   | @#55EE55: $f:I\to C$ |
| @#55EE55: postulate   | @#55EE55: $X \subseteq \bigcup_{i\in I,\ f}C_i$ |

==== Discussion ====
where we have some indexing via a set $I$.
==== Parents ====
=== Requirements ===
[[Indexed union]]