code: function(callback) {
              if (callback) {
                  var name = this.name
                  var indices = this.indexer.all();
                  var keys = [];
                  //Checking for the support of map.
                  if(Array.prototype.map) {
                      keys = indices.map(function(r){ return r.replace(name + '.', '') })
                  } else {
                      for (var key in indices) {
                          keys.push(key.replace(name + '.', ''));
                      }
                  }
                  this.fn('keys', callback).call(this, keys)
              }
              return this // TODO options for limit/offset, return promise
          }
docs: accepts [options], callback