Bugbear: Add Mutable Parameter fixes (#9682)

Part of #9366

Adds in fixes for B006 and B008, both relating to mutable parameter lint errors.

Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>

1 files changed, 5 insertions, 2 deletions

diff --git a/tests/test_visibility.py b/tests/test_visibility.py
index 510b630114..1b4dd47a82 100644
--- a/tests/test_visibility.py
+++ b/tests/test_visibility.py
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+from typing import Optional
 
 from mock import Mock
 
@@ -147,9 +148,11 @@ class FilterEventsForServerTestCase(tests.unittest.TestCase):
         return event
 
     @defer.inlineCallbacks
-    def inject_room_member(self, user_id, membership="join", extra_content={}):
+    def inject_room_member(
+        self, user_id, membership="join", extra_content: Optional[dict] = None
+    ):
         content = {"membership": membership}
-        content.update(extra_content)
+        content.update(extra_content or {})
         builder = self.event_builder_factory.for_room_version(
             RoomVersions.V1,
             {