json_schema: {
      "$schema": "http://json-schema.org/draft-04/schema#",
      "title": "tbox",
      "description": "A tbox atom",
      "type": "object",
      "properties": {
          "modifier": {
              "description": "A pattern modifier",
              "enum": [
                  "",
                  "dark"
              ]
          },
          "children": {
              "type": "string"
          },
          "content": {
              "type": "string"
          }
      },
      "anyOf": [
          {
              "required": [
                  "children"
              ]
          },
          {
              "required": [
                  "content"
              ]
          }
      ]
  }