[
  {
    "target": "b",
    "blocker": "{a}",
    "marker": "m:1:0"
  },
  {
    "target": "b",
    "blocker": "{a,c}",
    "marker": "m:1:1"
  },
  {
    "target": "c",
    "blocker": "{a}",
    "marker": "m:2:0"
  },
  {
    "target": "c",
    "blocker": "{b}",
    "marker": "m:2:1"
  },
  {
    "target": "c",
    "blocker": "{a,b}",
    "marker": "m:2:2"
  }
]