docs: function (query) {
              var rootCollection = this.getRoot();
  
              if (query instanceof Query) {
  
                  var options = _.defaults({}, {
                      query: query,
                      root: rootCollection
                  }, rootCollection.$);
  
                  var filterCacheId = query.whereCacheId(),
                      cache = rootCollection.$filterCache;
  
                  if (filterCacheId) {
                      if (!cache[filterCacheId]) {
                          cache[filterCacheId] = this._createFilteredCollection(query, options);
                      }
  
                      return cache[filterCacheId];
                  }
  
              }
  
              return rootCollection;
          }