{
  "@context": "http://www.w3.org/ns/shex.jsonld",
  "type": "Schema",
  "shapes": [
    {
      "id": "http://a.example/Sext",
      "type": "ShapeDecl",
      "shapeExpr": {
        "type": "ShapeExternal"
      }
    }
  ]
}