code: function(clientId, options) {
    events.EventEmitter.call(this);
  
    this.versions = null;
    this.indexes = null;
    this.memory = {};
  
    options = options || {};
    if (typeof options === 'string') {
      options = { path: options };
    }
    this.params = {
      clientId: clientId,
      path: options.path ? String(options.path) : '',
      storage: options.storage || DEFAULT_STORAGE,
      writePerms: options.writePerms || DEFAULT_WRITE_PERMS,
      indexLimit: options.indexLimit || DEFAULT_INDEX_LIMIT,
    };
  
    if (this.params.storage !== 'memory') {
      throw new Error(this.params.storage + ' storage is not currently supported');
    }
  }
docs: Cache constructor
  
  @param  string clientId
  @param  array options