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