Writes succeed even when query fail()s

This may be a fundamental limitation of the non-transactional design of TinkerGraph, in which case I would request a more detailed writeup on the fail() step itself.

I am trying to test a query where if all edges are removed from a vertex, the query should fail (to avoid an orphaned resource):

// drop some edges
.select('v').coalesce(__.in('Manages').limit(1), fail('all edges removed'))

In Neptune, the fail() step results in a rollback of the entire query so that the edges are not removed. In TinkerGraph, the query still fails (and I get my expected HTTP 409 response), but the graph changes are applied.

If this is unavoidable (e.g., no ability to roll back state once a drop() has been executed), then please add a note to the reference documentation for fail() mentioning that whether changes up to that point persist is implementation-specific.