arango> a1 = db.example.save({ a : 1 });
{ "_id" : "116308/4214943", "_rev" : 4214943 }
arango> db._delete(a1);
true
arango> db._delete(a1);
JavaScript exception in file '(arango)' at 1,4: [ArangoError 1202: document not found: cannot delete document]
!db._delete(a1);
!   ^
arango> db._delete(a1, true);
false