These methods express queries that are currently able to be expressed
with a sequence of In, Out and And queries. However, the constructed
filter approach is potentially significantly more expensive and are
more complex to reason about. For example it is often possible to make
the following re-writes,
p.Out(cond).In(cond).And(p) => p.HasAllOut(cond')
and
p.In(cond).Out(cond).And(p) => p.HasAllIn(cond').
The expense comes when reaching out to a commonly connected node and then
coming back; the return traversal will generate a large set of fruitless
candidates that then need to be filtered via the conjunction. This saves
that fruitless effort.
This is a very simplified version of a Gremlin-like language. The
simplification is in part forced by Go, but also reduces the level
of hiding complexity that is present in Gremlin.
