{
"type":"Topology",
"arcs": [
[[0.0, 0.0], [10, 0], [0, 10]]
],
"objects": {
"a_layer" : {"type": "GeometryCollection", "geometries" : [ {"type": "LineString", "arcs": [0, -1] } ] },
"foo" : {"type": "LineString", "arcs": [0, -1], "id" : "1" }
}
}