arango> db.relation.inEdges("86294/1528086");
[ ]
arango> db.relation.inEdges("86294/1593622");
[
  {
    "_id" : "1659158/3100950",
    "_rev" : 3100950, 
    "_from" : "86294/1528086",
    "_to" : "86294/1593622",
    "label" :
    "knows"
  }
]