text: define([], function() {
  
    /** Used as a safe reference for `undefined` in pre-ES5 environments. */
    var undefined;
  
    /**
     * Gets the cached value for `key`.
     *
     * @private
     * @name get
     * @memberOf _.memoize.Cache
     * @param {string} key The key of the value to get.
     * @returns {*} Returns the cached value.
     */
    function mapGet(key) {
      return key == '__proto__' ? undefined : this.__data__[key];
    }
  
    return mapGet;
  });
  