Reiterables x 12.

This commit is the next in a commit chain deeply type-checking
**reiterables** (i.e., collections satisfying the
`collections.abc.Collection` protocol with guaranteed `O(1)` read-only
access to *only* the first collection item), en-route to *finally*
resolving feature request #167 kindly submitted by the perennial
brilliant @langfield (...*how I miss that awesome guy!*) several
lifetimes ago back when I was probably a wandering vagabond Buddhist
monk with a bad attitude, a begging bowl the size of my emaciated torso,
and an honestly pretty cool straw hat that glinted dangerously in the
firelight. Note that reiterables include *all* containers matched by one
or more of the following PEP 484- or 585-compliant type hints:

* `frozenset[...]`.
* `set[...]`.
* `collections.deque[...]`.
* `collections.abc.Collection[...]`.
* `collections.abc.KeysView[...]`.
* `collections.abc.MutableSet[...]`.
* `collections.abc.Set[...]`.
* `collections.abc.ValuesView[...]`.
* `typing.AbstractSet[...]`.
* `typing.Collection[...]`.
* `typing.Deque[...]`.
* `typing.FrozenSet[...]`.
* `typing.KeysView[...]`.
* `typing.MutableSet[...]`.
* `typing.Set[...]`.
* `typing.ValuesView[...]`.

Specifically, this commit continues exercising this shadow madness with
The Litany of Unit Tests from Hell that Remain Nameless. They will never
end... yet the end is in site. End of commit chain, ahoy! (*Vast mast!*)