small refactor

src/borgstore/store.py

@@ -80,11 +80,11 @@ def close(self) -> None:
     def _stats_updater(self, key):
         """update call counters and overall times, also emulate latency and bandwidth"""
         # do not use this in generators!
-        volume_before = self._stats.get(f"{key}_volume", 0)
+        volume_before = self._stats_get_volume(key)
         start = time.perf_counter_ns()
         yield
         be_needed_ns = time.perf_counter_ns() - start
-        volume_after = self._stats.get(f"{key}_volume", 0)
+        volume_after = self._stats_get_volume(key)
         volume = volume_after - volume_before
         emulated_time = self.latency + (0 if not self.bandwidth else float(volume) / self.bandwidth)
         remaining_time = emulated_time - be_needed_ns / 1e9
@@ -97,6 +97,9 @@ def _stats_updater(self, key):
     def _stats_update_volume(self, key, amount):
         self._stats[f"{key}_volume"] += amount
 
+    def _stats_get_volume(self, key):
+        return self._stats.get(f"{key}_volume", 0)
+
     @property
     def stats(self):
         """