code: function checkDependencies(req, res) {
                      var modelName = req.params.modelName,
                          id = req.params.documentId,
                          models = _.pluck(registry.models, 'model');
  
                      dependencies.check(models, modelName, id, function (err, depPair) {
                          if (err) throw err;
                          if (_.isEmpty(depPair)) return res.json(200, []);
                          var deps = depPair[1];
                          var lines = dependencies.depsToLines(deps);
                          return res.json(200, lines);
                      });
                  }
docs: in use by document->delete button (1)