Nested Context doesn't work #264

Hello,

I'm trying to generate JSON-LD from an object with relationship-id to another one:

Object1{
String id
String prop1
String relationshipId
}

For the relationshipId, I defined another Base in the @context, so that I can store it in a different RDF graph. It worked well in the jsonld playground.

But, the base from the nested context is not inserted by the jsonld-java.

Please help.