docs: function filterBy(dependentKey, propertyKey, value) {
      var callback;
  
      if (arguments.length === 2) {
        callback = function (item) {
          return _emberMetalProperty_get.get(item, propertyKey);
        };
      } else {
        callback = function (item) {
          return _emberMetalProperty_get.get(item, propertyKey) === value;
        };
      }
  
      return filter(dependentKey + '.@each.' + propertyKey, callback);
    }