code: def _invalidate_entry(self, key):
          "If exists: Invalidate old entry and return it."
          old_entry = self.access_lookup.get(key)
          if old_entry:
              old_entry.is_valid = False
  
          return old_entrf _invalidate_entry(self, key):
          "If exists: Invalidate old entry and return it."
          old_entry = self.access_lookup.get(key)
          if old_entry:
              old_entry.is_valid = False
  
          return old_entry
docs: If exists: Invalidate old entry and return it.