arangosh> db._create("mycollection")
[ArangoCollection 451408779, "mycollection" (type document, status loaded)]
arangosh> db.mycollection.save({ _key: "testKey", Hello : "World" })
{ 
  "_id" : "mycollection/testKey", 
  "_rev" : "451736459", 
  "_key" : "testKey" 
}
arangosh> db._query('FOR my IN mycollection RETURN my._key').toArray()
[ 
  "testKey" 
]