Use .as_str_seq() instead of .get().
@@ -156,7 +156,7 @@ def apply_metadata(album_info, mapping):
'data_source',):
# Don't overwrite fields with empty values unless the
# field is explicitly allowed to be overwritten
- clobber = field not in config['no_clobber'].get()
+ clobber = field not in config['no_clobber'].as_str_seq()
value = getattr(album_info, field)
if value is None and not clobber:
continue
