def METHOD_NAME(self):
    # Check if the cost map is updated -> local map for navigation is working
    def on_cost_map_message_received(message):
        # There should be a value in the range ]0, 100]
        for value in message.data:
            if value > 0 and value <= 100:
                return True
        return False
    self.wait_for_messages(self.__node, OccupancyGrid, '/global_costmap/costmap', condition=on_cost_map_message_received)