"alignment_mark": {
  "type": "object",
  "additionalProperties": false,
  "required": [
    "type",
    "attrs"
  ],
  "properties": {
    "type": {
      "enum": ["alignment"]
    },
    "attrs": {
      "type": "object",
      "additionalProperties": false,
      "required": ["align"],
      "properties": {}
    }
  }
}

 "type": {
  "enum": ["alignment"]
}

 "attrs": {
  "type": "object",
  "additionalProperties": false,
  "required": ["align"],
  "properties": {
    "align": {
      "enum": [
        "center",
        "end"
      ]
    }
  }
}

 "align": {
  "enum": [
    "center",
    "end"
  ]
}