{
  "@context": {
    "@vocab": "http://example.org/",
    "input": {"@container": ["@graph", "@id"]}
  },
  "input": {
    "http://example.com/g1": [{"value": "x"}, {"value": "y"}],
    "http://example.com/g2": [{"value": "a"}, {"value": "b"}]
  }
}