Language is ignored

[pheyvaer]

The SPARQL query does not contain the language tags.

Context is

{
  "@context": {
    "foaf": "http://xmlns.com/foaf/0.1/",
    "givenName": {
      "@id": "foaf:givenName",
      "@language": "en"
    },
    "familyName": {
      "@id": "foaf:familyName",
      "@language": "en"
    },
    "img": {
      "@id": "foaf:img"
    }
  }
}

The GraphQL-LD query is

{
  givenName @single
  familyName @single
  img @single
}