{
  "vertices": [
    "s",
    "a",
    "t"
  ],
  "balances": {
    "s": 1,
    "a": 0,
    "t": -1
  },
  "arcs": [
    {
      "id": "via-a",
      "tail": "s",
      "head": "a",
      "lower": 0,
      "upper": 1
    },
    {
      "id": "a-to-t",
      "tail": "a",
      "head": "t",
      "lower": 0,
      "upper": 1
    },
    {
      "id": "direct",
      "tail": "s",
      "head": "t",
      "lower": 0,
      "upper": 1
    }
  ]
}