code: function(options) {
    FunctionParameter.call(this, options);
    this.regionParameter = options.regionParameter;
    this.value = "";
    this._subtype = undefined;
  }
docs: A parameter that specifies an arbitrary polygon on the globe.
  
  @alias GeoJsonParameter
  @constructor
  @extends FunctionParameter
  
  @param {Object} options Object with the following properties:
  @param {Terria} options.terria The Terria instance.
  @param {String} options.id The unique ID of this parameter.
  @param {String} [options.name] The name of this parameter. If not specified, the ID is used as the name.
  @param {String} [options.description] The description of the parameter.
  @param {Boolean} [options.defaultValue] The default value.