def process_tree(self, channel_node):
        """
        Returns a list of all file names associated with a tree. Profiling suggests using a global list with `extend`
        is faster than using a global set or deque.
        :param channel_node: Root node of the channel being processed
        :return: The list of unique file names in `channel_node`.
        """
        file_names = []
        self.process_tree_recur(file_names, channel_node)
        return [x for x in set(file_names) if x]
Returns a list of all file names associated with a tree. Profiling suggests using a global list with `extend`
        is faster than using a global set or deque.
        :param channel_node: Root node of the channel being processed
        :return: The list of unique file names in `channel_node`.