code: def test_get_message_headers_non_pika_broker():
      event_broker = Mock()
      exporter = MockExporter(event_broker=event_broker)
  
      # noinspection PyProtectedMember
      assert exporter._get_message_headers() is None
  
file_path: rasa/tests/core/test_exporter.py
imports: import uuid
  from pathlib import Path
  from typing import Any, AsyncIterator, Dict, Optional, Text, List
  from unittest.mock import Mock
  import pytest
  from rasa.shared.core.constants import ACTION_SESSION_START_NAME
  from rasa.shared.core.domain import Domain
  from rasa.core.brokers.pika import PikaEventBroker
  from rasa.core.brokers.sql import SQLEventBroker
  from rasa.core.constants import RASA_EXPORT_PROCESS_ID_HEADER_NAME
  from rasa.shared.core.events import Event, SessionStarted, ActionExecuted
  from rasa.core.tracker_store import SQLTrackerStore
  from rasa.shared.core.trackers import DialogueStateTracker
  from rasa.exceptions import NoConversationsInTrackerStoreError, NoEventsToMigrateError, PublishingError
  from tests.conftest import MockExporter, random_user_uttered_event, AsyncMock
label_desc: Use image node_id 2 for calling a global function with example usage: test_get_message_headers_non_pika_broker() without return types