uplinks

In std/graph.

fn uplinks(x: Option<Doc>) : List<Edge>
fn uplinks(x: Doc) : List<Edge>
fn uplinks(x: Hit<Card>) : List<Edge>
fn uplinks(xs: Collection<Doc>) : List<Edge>
fn uplinks(xs: Collection<Hit<Card>>) : List<Edge>

The edges of the links x writes to other cards: one Edge per authored link, its source the card x. Over a hit, the card it holds; over an absent card, none; over a collection, every element's, in order.