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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 _new_level(self, depth):
 """Create a new level and header and connect signals :param depth: the depth level :type depth: int :returns: None :rtype: None :raises: None """

        l = self.create_level(depth)
        h = self.create_header(depth)
        self.add_lvl_to_ui(l, h)
        l.new_root.connect(partial(self.set_root, depth+1))
        self._levels.append(l)