    graph.isNeighbor(elementA, elementB [, opt])

Return `true` if `elementB` is a neighbor of `elementA`. A neighbor of an element is another element connected to it via an inbound and/or outbound link.

Accepts several options, which may be provided inside an `opt` object:

- `deep` - return `true` also if `elementB` is a neighbor of an element embedded in `elementA`.
- `outbound` - return `true` only if `elementB` is a succeeding neighbor of `elementA`. For example, if `elementB` is connected to a directed link behind the connection of `elementA`.
- `inbound` - return `true` only if `elementB` is a preceding neighbor `elementA`. For example, if `elementB` is connected to a directed link ahead of the connection of `elementA`.
- `indirect` - in addition to standard rules (including `deep`/`outbound`/`inbound` modifications), also return `true` if `elementB` can only be considered a neighbor of `elementA` if we go against the flow of directed links at link-link connections.