// expect: error form a loop
// a loop through a module needs a deferred block too, as in the graph itself
{ "format": "maszyna-vehicle-graph", "version": 2,
  "nodes": [ { "id": "m", "type": "module", "params": { "file": "modules/inverter.vhgm" } } ],
  "connections": [ { "from": "m.q", "to": "m.a" } ] }