code: function(key) {
  			var j = this._indexOfKey(key),
  				rest = this._keys.slice(j + 1);
  
  			delete this._keyMap[key];
  
  			for (var k in this._keyMap) {
  				if (j < this._keyMap[k]) {
  					this._keyMap[k] -= 1;
  				}
  			}
  			
  			this._keys.length = j;
  			this._keys = this._keys.concat(rest);
  			this.length = this._keys.length;
  		}
docs: Removes a key from the keys array.
  @method _removeKey
  @param key {String} Required. The key to remove.
  @protected