Able to create duplicate edge with multiplicity SIMPLE

[krittamk]

As per my understanding of janusgraph docs there can only be at most one edge of multiplicity SIMPLE between two vertices.

I'm trying to represent a 'friend' relationship here i.e. if A is a friend of B, B is also a friend of A (undirected relationship).

But in practice I've been able to create two edges between A and B

A ---->B
B ---->A

m = graph.openManagement()
gremlin> m.getEdgeLabel("friend").multiplicity()
==>SIMPLE

v1 = g.addV("person").property("id","qazwsx").next()
==>v[1724552]
gremlin> v2 = g.addV("person").property("id","xswzaq").next()
==>v[1728648]
gremlin> e1 = g.V(v1).addE("friend").to(v2).next()
==>e[ivwx-10yo8-1lh-111u0][1724552-friend->1728648]
gremlin> e2 = g.V(v2).addE("friend").to(v1).next()
==>e[iwb5-111u0-1lh-10yo8][1728648-friend->1724552]

Please resolve this confusion.
In any case how do i enforce such a schema ?

[vtslab]

This is intended behavior, but the wording in the reference documents is ambiguous. So, pair (v1, v2) != pair (v2, v1). You can also check in the source code that the uniqueness check works this way (line716):
https://github.com/JanusGraph/janusgraph/blob/v0.5.3/janusgraph-core/src/main/java/org/janusgraph/graphdb/transaction/StandardJanusGraphTx.java
Also note that in a distributed system one could not prevent two independent transactions to create edges in both directions concurrently, because there is nothing yet than can be locked (see ref docs on locking).