pub(crate) fn set_neighbours<'s, 'b>(
v: &Vertex<'s, 'b>,
alloc: &'b Bump,
seen: &mut HashMap<&Vertex<'s, 'b>, SmallVec<[&'b Vertex<'s, 'b>; 2]>, BuildHasherDefault<FxHasher>>
)Expand description
Compute the neighbours of v if we haven’t previously done so,
and write them to the .neighbours cell inside v.