function $Refs () {
/**
 * Indicates whether the schema contains any circular references.
 *
 * @type {boolean}
 */
this.circular = false;

/**
 * A map of paths/urls to {@link $Ref} objects
 *
 * @type {object}
 * @protected
 */
this._$refs = {};

/**
 * The {@link $Ref} object that is the root of the JSON schema.
 *
 * @type {$Ref}
 * @protected
 */
this._root$Ref = null;
}
This class is a map of JSON references and their resolved values.