Refactor: extract new method is_chunk_used_by_anyone

1 files changed, 4 insertions, 1 deletions

diff --git a/obnamlib/fmt_ga/indexes.py b/obnamlib/fmt_ga/indexes.py
index babc2e4b..ac22cb61 100644
--- a/obnamlib/fmt_ga/indexes.py
+++ b/obnamlib/fmt_ga/indexes.py
@@ -199,9 +199,12 @@ class GAChunkIndexes(object):
         return [
             chunk_id
             for chunk_id in self._used_by_tree.keys()
-            if self._used_by_tree.lookup(chunk_id) == []
+            if not self.is_chunk_used_by_anyone(chunk_id)
         ]
 
+    def is_chunk_used_by_anyone(self, chunk_id):
+        return self._used_by_tree(chunk_id) != []
+
     def get_bags_contianing_chunks(self, chunk_store, chunk_ids):
         return set(
             chunk_id