content: {
    "$defs": {
      "TestNullable": {
        "additionalProperties": false,
        "properties": {
          "child1": {
            "oneOf": [
              {
                "type": "string"
              },
              {
                "type": "null"
              }
            ]
          }
        },
        "required": [
          "child1"
        ],
        "type": "object"
      }
    },
    "$id": "https://github.com/invopop/jsonschema/test-nullable",
    "$ref": "#/$defs/TestNullable",
    "$schema": "https://json-schema.org/draft/2020-12/schema"
  }