code: function MemoryStore (options) {
    options = options || {};
  
    options.max = Number(options.max);
    if (isNaN(options.max)) options.max = DEFAULT_MAX;
    this._max = options.max;
  
    options.gcProbability = Number(options.gcProbability);
    if (isNaN(options.gcProbability)) options.gcProbability = DEFAULT_PROBABILITY;
    this._gcProbability = options.gcProbability;
  
    debug('init: max=%s, gcProbability=%s', this._max, this._gcProbability);
  
    this._keys = {};
    this._keyTotal = 0;
  
    return this;
  }
docs: MemoryStore
  
  @param {Object} options
  - {Number} max
  - {Number} gcProbability