Add the given item as children

def append(self, item):
        """
        Add the given item as children
        """
        if self.url:
            raise TypeError('Menu items with URL cannot have childrens')

        # Look for already present common node
        if not item.is_leaf():
            for current_item in self.items:
                if item.name == current_item.name:
                    for children in item.items:
                        current_item.append(children)
                    return

        # First insertion
        self.items.append(item)