>>> fields_with_save_methods = [field for field in objects.Instance.fields if field != 'tags']
>>> fields_with_save_methods
['vm_state', 'pci_requests', 'availability_zone', 'terminated_at', 'ephemeral_gb', 'old_flavor', 'user_data', 'numa_topology', 'pci_devices', 'display_description', 'cleaned', 'vm_mode', 'flavor', 'deleted_at', 'reservation_id', 'id', 'security_groups', 'disable_terminate', 'root_device_name', 'display_name', 'uuid', 'default_swap_device', 'info_cache', 'hostname', 'deleted', 'launched_on', 'ec2_ids', 'key_data', 'kernel_id', 'config_drive', 'power_state', 'default_ephemeral_device', 'progress', 'created_at', 'project_id', 'launched_at', 'scheduled_at', 'node', 'ramdisk_id', 'access_ip_v6', 'access_ip_v4', 'vcpu_model', 'key_name', 'updated_at', 'host', 'root_gb', 'user_id', 'system_metadata', 'task_state', 'shutdown_terminate', 'cell_name', 'ephemeral_key_uuid', 'locked', 'fault', 'instance_type_id', 'locked_by', 'launch_index', 'memory_mb', 'vcpus', 'image_ref', 'architecture', 'auto_disk_config', 'os_type', 'metadata', 'new_flavor']