code: function (collection, element, settings) {
              if (settings.children) {
                  $.each(settings.children, function (index, childrenSettings) {
                      if (!childrenSettings.selector) {
                          console.log("jquery.collection.js: given collection " + collection.attr('id') + " has children collections, but children's root selector is undefined.");
                          return true;
                      }
                      if (element !== null) {
                          element.find(childrenSettings.selector).collection(childrenSettings);
                      } else {
                          collection.find(childrenSettings.selector).collection(childrenSettings);
                      }
                  });
              }
          }
docs: this plugin supports nested collections, and this method enables them when the parent collection is initialized. see http://symfony-collection.fuz.org/symfony3/advanced/collectionOfCollections