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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 construct_channel(self, **kwargs):
 """ Build the channel tree by adding TopicNodes and ContentNode children. """

        channel = self.get_channel(**kwargs)
        json_tree_path = self.get_json_tree_path(**kwargs)
        json_tree = read_tree_from_json(json_tree_path)
        build_tree_from_json(channel, json_tree['children'])
        raise_for_invalid_channel(channel)
        return channel