at.tensei.pipeline

Nodes and wires (§6). `wires` is required and is not declared: an array of [from, to] pairs of node ids, and the lexicon language has no array of arrays. Also not stated by the lexicon, and enforced by the validator (§6.1): node ids are unique; the graph is acyclic, has exactly one output reachable from every source, a source has no inbound wire and every other node exactly one, except a union, which has two or more; an output has no outbound wire; every source's mapping declares exactly the initial `slots`; every field a node names is in the shape of its incoming wire; and `presentation` names fields of the output's shape.