anchor.diff:  g.V().has('name','2016').out('may').out('day31').as('start').
     V().has('name','2016').out('june').out('day01').as('end').
     emit().repeat(__.in('next')).until(where(eq('start'))).
  -  out('has').order().by('name').values('name')                            <4>
  +  out('has').
  +  order().by('name').values('name')                                       <4>
   ----
   
   <1> Find all the events in 2016.
  
positive.code: 
  [gremlin-groovy,existing]
  ----
  g.withComputer().V().has('name', within(input)).aggregate('input').
    has('name', input.head()).repeat(out('hasParent')).emit().as('x').
    select('input').unfold().has('name', within(input.tail())).
    repeat(out('hasParent')).emit(where(eq('x'))).
    group().by(select('x')).by(path().count(local).fold()).
    unfold().filter(select(values).count(local).is(input.tail().size())).
    order().by(select(values).unfold().sum()).
    select(keys).limit(1).valueMap(true)
  ----
  
  Maximum Depth
  ~~~~~~~~~~~~~
  
negative.code:   repeat(out('hasParent')).emit().as('x').                               <1>
    V().has('name', within(input.tail())).                                 <2>
    repeat(out('hasParent')).emit(where(eq('x'))).                         <3>
    group().
      by(select('x')).
      by(path().count(local).fold()).                                      <4>
    unfold().filter(select(values).count(local).is(input.tail().size())).  <5>
    order().by(select(values).
    unfold().sum()).                                                       <6>
    select(keys).limit(1).valueMap(true)                                   <7>
  ----
  
  