code: function(api, id, key) {
    // get storage object
    var obj = _getStorageObject(api, id);
    if(obj !== null && key in obj) {
      // remove key
      delete obj[key];
  
      // see if entry has no keys remaining
      var empty = true;
      for(var prop in obj) {
        empty = false;
        break;
      }
      if(empty) {
        // remove entry entirely if no keys are left
        obj = null;
      }
  
      // set storage object
      _setStorageObject(api, id, obj);
    }
  }
docs: Removes an item from local storage.
  
  @param api the storage interface.
  @param id the storage ID to use.
  @param key the key for the item.