Angular: Ordering Child Rows

http://angularjs.org/

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css">
<div ng-controller="MyCtrl" ng-style="{color: myColor}">
<table class="table table-striped table-hover table-responsive">
        <thead>
            <th>Código</th>
            <th>Descrição</th>
            <th>Código Pai</th>
        </thead>
        <tbody>
            <tr ng-repeat="natureza in naturezas | filter:filterExpression | orderBy:'codNat'" ng-click="toggleCustom(natureza)">
                <td>{{natureza.codNat}}</td>
                <td>{{natureza.descrNat}}</td>
                <td align="right">{{natureza.codNatPai}}</td>
            </tr>
            
        </tbody>
    </table>
</div>

JavaScript

var myApp = angular.module('myApp', []);

function MyCtrl($scope) {
    var codNatPai = [];
    
    $scope.naturezas = [
        {
            codNat: '100000',
            descrNat: 'Natureza 1',
            codNatPai: '0'
        },
        {
            codNat: '200000',
            descrNat: 'Natureza 2',
            codNatPai: '0'
        },
        {
            codNat: '110000',
            descrNat: 'Natureza 1.1',
            codNatPai: '100000'
        },
        {
            codNat: '120000',
            descrNat: 'Natureza 1.2',
            codNatPai: '100000'
        },
        {
            codNat: '210000',
            descrNat: 'Natureza 2.1',
            codNatPai: '200000'
        },
        {
            codNat: '220000',
            descrNat: 'Natureza 2.2',
            codNatPai: '200000'
        },
        {
            codNat: '111000',
            descrNat: 'Natureza 1.1.',
            codNatPai: '110000'
        }
    ];
    
    $scope.filterExpression = function(i) {
        
      return (i.codNatPai == 0 || codNatPai.indexOf(i.codNatPai)>-1 );
    }
    $scope.custom = true;
    $scope.toggleCustom = function(i){
        var n = codNatPai.indexOf(i.codNat);
        if (n<0) {
            codNatPai.push(i.codNat);
        } else {
            codNatPai.splice(n);
        }
        console.log(n,codNatPai);
            
    }
    $scope.buscar = function(i){
        alert("Selected: " + i.codNat)
    }
}