The most simple dataset description we have figured out is a sequence of maps.

Using this definition, things like k-fold have natural interpretations.

While this works well for clojure generation/manipulation,  ML interfaces uniformly
require this sequence to be coalesced somehow into larger buffers; sometimes on a
point by point basis and sometimes into batching buffers.  This file is intended
to provide direct, simple tools to provide either type of coalesced information.

Care has been taken to keep certain operations lazy so that datasets of unbounded
length can be manipulated.