pub const SET: BuiltinSchema;Expand description
Set<T>: an immutable set, kept in ascending element order.
contains is the very declaration Array and Vector answer membership
with, shared rather than restated, because it is the same question about
a different container — ARRAY says the rest of it. There is no
indexOf or slice here: the ascending order is how a set is stored
rather than an order a caller chose, and toArray() is where a program
says it wants that order to be its own.