Python offers several stateful collections, including the set collection. For our purposes, there are two use cases for a set: a stateful set that accumulates items, and frozenset that is used to optimize searches for an item.
We can create frozenset from an iterable in the same way we create a tuple object from an iterable fronzenset(some_iterable) method; this will create a structure that has the advantage of a very fast in operator. This can be used in an application that gathers data, creates a set, and then uses that frozenset to process some other data items.
We may have a set of colors that we will use as a kind of chroma-key: we will use this color to create a mask that will be used to combine two images. Pragmatically, ...
