{
  "@context": {
    "@vocab": "http://example/",
    "idmap": {"@container": "@id", "@nest": "nestedidmap"},
    "nestedidmap": "@nest"
  },
  "nestedidmap": {
    "idmap": {
      "http://example.org/foo": {"label": "Object with @id <foo>"},
      "_:bar": {"label": "Object with @id _:bar"}
    }
  }
}