When is the libvirt connection closed

[qixinwuchen]

` def __connect_socket(self):
uri = "qemu:///system"

    try:
        self.connection = libvirt.open(uri)
        self.last_error = None

    except libvirtError as e:
        self.last_error = f"Connection Failed: {str(e)}"
        self.connection = None`

the connection is opened here, but when the connection is closed?