def gateway_ip(self, container_id: str) -> str:
        """
        Get the gateway ip address for a container.
        """
        container = self.get_container(container_id)
        network_name = self.network_name(container_id)
        return str(container["NetworkSettings"]["Networks"][network_name]["Gateway"])

        Get the gateway ip address for a container.
        
core/testcontainers/core/docker_client.py