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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add(self, text, checked=False, sort=None):
 """Add a new item to the list. Args: text (str):
 The text. checked (bool):
 Whether this item is checked. sort (int):
 Item id for sorting. """

        node = ListItem(parent_id=self.id, parent_server_id=self.server_id)
        node.checked = checked
        node.text = text
        if sort is not None:
            node.sort = sort
        self.append(node, True)
        self.touch(True)
        return node