json_schema: {
      "additionalProperties": false,
      "description": "Schema for a form field's value being changed",
      "properties": {
          "elementClasses": {
              "description": "An array of the classes on the element",
              "items": {
                  "description": "A class on the element",
                  "maxLength": 4096,
                  "minLength": 0,
                  "type": "string"
              },
              "type": "array"
          },
          "elementId": {
              "description": "The id of the element that has just received focus",
              "maxLength": 4096,
              "minLength": 0,
              "type": "string"
          },
          "formId": {
              "description": "The id of the form the element belongs to",
              "maxLength": 4096,
              "minLength": 0,
              "type": "string"
          },
          "nodeName": {
              "description": "The node type of the element",
              "enum": [
                  "INPUT",
                  "TEXTAREA",
                  "SELECT"
              ],
              "type": "string"
          },
          "type": {
              "description": "The type of input element",
              "enum": [
                  "button",
                  "checkbox",
                  "color",
                  "date",
                  "datetime",
                  "datetime-local",
                  "email",
                  "file",
                  "hidden",
                  "image",
                  "month",
                  "number",
                  "password",
                  "radio",
                  "range",
                  "reset",
                  "search",
                  "submit",
                  "tel",
                  "text",
                  "time",
                  "url",
                  "week"
              ],
              "type": [
                  "string",
                  "null"
              ]
          },
          "value": {
              "description": "The value of the element when it gained focus",
              "maxLength": 65535,
              "minLength": 0,
              "type": [
                  "string",
                  "null"
              ]
          }
      },
      "required": [
          "formId",
          "elementId",
          "nodeName",
          "value"
      ],
      "self": {
          "format": "jsonschema",
          "name": "change_form",
          "vendor": "com.snowplowanalytics.snowplow",
          "version": "1-0-0"
      },
      "type": "object"
  }