@json type is not supported #319

  "@id":"resource:some-new-guid-for-the-context",
  "@graph":[
    {
      "@id":"resource:some-new-guid-for-the-annotated-document-resource",
      "@type":"AnnotatedDocument",
      "document":{
        "sections":[
          {
            "id":"section-1",
            "author":"Jeff Bezos",
            "content":"Billionaire Jeff Bezos blasted into space on Tuesday, in the first crewed flight of his rocket ship, New Shepard.\nHe was accompanied by Mark Bezos, his brother, Wally Funk, an 82-year-old pioneer of the space race, and an 18-year-old student.\nThey travelled in a capsule with the biggest windows flown in space, offering stunning views of the Earth.\nAll four passengers have now parachuted safely back to Earth after their 10-minute, 10-second trip.\nNew Shepard, built by Bezos' company Blue Origin, is designed to serve the burgeoning market for space tourism among the super-wealthy.\nOn this flight was the oldest person who has been to space - Ms Funk - and the youngest, student Oliver Daemen.\nThe spacecraft lifted off at 14:12 BST (09:12 EDT) from a private launch site near Van Horn, Texas."
          },
          {
            "id":"section-2",
            "author":"other guy"
          }
        ],
        "@id":"some-artif-id",
        "@type":"Article",
        "author":"Unknown"
      },
      "annotations":[
        {
          "motivation":"tagging",
          "@type": "Annotation",
          "@id":"resource:c6d6141f-0f67-4726-ade9-6e22b193038d",
          "body":{
            "@type":"Person",
            "annotationSetName":"Novelties",
            "overallScore":"0.7487862501122519",
            "@id":"resource:50d0b3a9-015e-44a5-917d-9970e152fa50"
          },
          "target":{
            "@type":"Text",
            "@id":"resource:a4078aca-e04b-419e-a588-f2da720de699"
          }
        }
      ]
    }
  ],
  "@context":[
    "http://www.w3.org/ns/anno.jsonld",
    {
      "document":"ontocontent:document",
      "annotations":"ontocontent:annotations",
      "ann":"http://data.ontotext.com/annotation/",
      "ontoa":"http://ontology.ontotext.com/annotation#",
      "ontocontent":"http://ontology.ontotext.com/content#",
      "onto":"http://ontology.ontotext.com/taxonomy/",
      "content":"http://data.ontotext.com/content/",
      "resource":"http://ontology.ontotext.com/resource/",
      "xsd":"http://www.w3.org/2001/XMLSchema#",
      "nif":"http://persistence.uni-leipzig.org/nlp2rdf/ontologies/nif-core#",
      "AnnotatedDocument":"ontocontent:AnnotatedDocument",
      "sections":{
        "@id":"onto:sections",
        "@type":"@json"
      },
      "Article":"ontocontent:Article",
      "author":{
        "@id":"ontocontent:author",
        "@type":"xsd:string"
      },
      "Person":"onto:Person",
      "annotationSetName":{
        "@id":"ontoa:annotationSetName",
        "@type":"xsd:string"
      },
      "overallScore":{
        "@id":"ontoa:overallScore",
        "@type":"xsd:double"
      }
    }
  ]
}

 InputStream inputStream = new FileInputStream(
        Main.class.getClassLoader().getResource("input.json").getFile());
    Object jsonObject = JsonUtils.fromInputStream(inputStream);
    Object o = JsonLdProcessor.toRDF(jsonObject, new JsonLdOptions());
    System.out.println(o);

com.github.jsonldjava.core.JsonLdError: invalid type mapping: @json
	at com.github.jsonldjava.core.Context.createTermDefinition(Context.java:371)
	at com.github.jsonldjava.core.Context.parse(Context.java:289)
	at com.github.jsonldjava.core.Context.parse(Context.java:150)
	at com.github.jsonldjava.core.Context.parse(Context.java:305)
	at com.github.jsonldjava.core.JsonLdApi.expand(JsonLdApi.java:550)
	at com.github.jsonldjava.core.JsonLdApi.expand(JsonLdApi.java:1027)
	at com.github.jsonldjava.core.JsonLdProcessor.expand(JsonLdProcessor.java:139)
	at com.github.jsonldjava.core.JsonLdProcessor.toRDF(JsonLdProcessor.java:528)
	at com.github.jsonldjava.core.JsonLdProcessor.toRDF(JsonLdProcessor.java:578)