Returns the children in this group.
        
        :return     [<QtGui.QListWidgetItem>, ..]

def children(self):
        """
        Returns the children in this group.
        
        :return     [<QtGui.QListWidgetItem>, ..]
        """
        new_refs = set()
        output = []
        for ref in self._children:
            item = ref()
            if item is not None:
                output.append(item)
                new_refs.add(ref)
        
        self._children = new_refs
        return output