Get the topological order of a CFG Node.

        :param cfg_node: A CFGNode instance.
        :return: An integer representing its order, or None if the CFGNode does not exist in the graph.

def get_topological_order(self, cfg_node):
        """
        Get the topological order of a CFG Node.

        :param cfg_node: A CFGNode instance.
        :return: An integer representing its order, or None if the CFGNode does not exist in the graph.
        """

        if not self._quasi_topological_order:
            self._quasi_topological_sort()

        return self._quasi_topological_order.get(cfg_node, None)