Appended test to improved functionality

passed black formatter
pytype doesn't work on Win10.

Author: lluchini

rasa/core/processor.py

@@ -36,7 +36,7 @@
     ReminderScheduled,
     SlotSet,
     UserUttered,
-    SessionStarted
+    SessionStarted,
 )
 from rasa.core.interpreter import (
     INTENT_MESSAGE_PREFIX,
@@ -176,9 +176,10 @@ async def _update_tracker_session(
             )
 
     async def get_tracker_with_session_start(
-        self, sender_id: Text,
+        self,
+        sender_id: Text,
         output_channel: Optional[OutputChannel] = None,
-        metadata: Optional[Dict] = None
+        metadata: Optional[Dict] = None,
     ) -> Optional[DialogueStateTracker]:
         """Get tracker for `sender_id` or create a new tracker for `sender_id`.
 

tests/core/test_actions.py

@@ -510,6 +510,21 @@ async def test_action_session_start_without_slots(
     assert events == [SessionStarted(), ActionExecuted(ACTION_LISTEN_NAME)]
 
 
+async def test_action_session_start_with_metada(
+    default_channel: CollectingOutputChannel,
+    template_nlg: TemplatedNaturalLanguageGenerator,
+    template_sender_tracker: DialogueStateTracker,
+    default_domain: Domain,
+):
+    template_sender_tracker.events.append(
+        SessionStarted(metadata={"metadataTestKey": "metadataTestValue"})
+    )
+
+    await test_action_session_start_without_slots(
+        default_channel, template_nlg, template_sender_tracker, default_domain
+    )
+
+
 @pytest.mark.parametrize(
     "session_config, expected_events",
     [