static fromJson(options) {
    // In this case we simply pass the JSON options along to the constructor,
    // but you can also use this to get message references, and other such things.
    // `this` might be a subclass of FieldTurtle if that class doesn't override
    // the static fromJson method.
    return new this(options['pattern'], options['hat'], options['turtleName']);
  }
The size of the area rendered by the field.
@type {Blockly.utils.Size}
@protected
@override