prepare_section.js

        MapAttrsToGroups : function (section) {
            var defer = $q.defer();
            var merged = [];
            var cache_groups = {};
            var elements = section.attr.elements;
            
            for (var i = 0; i < elements.length; i++) {
                var field = elements[i];
                if (!field.attr.group.id) {
                    merged.push(field);
                    
                } else {
                    var group = field.attr.group;
                    var id = group.id;
                    var groupAttr = cache_groups[id];
                    if (!groupAttr) {
                        groupAttr = cache_groups[id] = _getGroupAttr(group);
                        merged.push(groupAttr);
                    }
                    field.attr.group = "";

                    if (groupAttr.el == "group_matrix" || groupAttr.el == "group_list"){
                        groupAttr.attr.forms.push(field);
                    } else if (groupAttr.el == "group") {
                        groupAttr.attr.childs.push(field);
                    }
                    if(groupAttr.el == "group_matrix"){                        
                        groupAttr.attr.output.push(angular.copy(field));
                    }
                }
            };

            section.attr.elements = merged;
            defer.resolve(section);
            return defer.promise;
        },