diff --git a/podman-compose-backup.py b/podman-compose-backup.py
index c54e4de..77a81fa 100644
--- a/podman-compose-backup.py
+++ b/podman-compose-backup.py
@@ -32,6 +32,7 @@ import shlex
 import sys
 from typing import (
     Dict,
+    Iterable,
     List,
     Mapping,
     NewType,
@@ -122,6 +123,14 @@ PODMAN_COMPOSE_EXEC = CommandArgs(
 # === helpers
 
 
+def filter_cmds(command: Iterable[Optional[str]]) -> CommandArgs:
+    return CommandArgs([arg for arg in command if arg is not None])
+
+
+def combine_cmds(*commands: CommandArgs | List[Optional[str]]) -> CommandArgs:
+    return CommandArgs([arg for cmd in commands for arg in filter_cmds(cmd)])
+
+
 @wraps(print)
 def error(*args, **kwargs):
     ret = print(*args, file=sys.stderr, **kwargs)