new_contents: import unittest
  import copy
  from unittest.mock import Mock
  
  import chat_plugin
  from chat_plugin import handle_conversation_after_delete
  
  class TestHandleConversationAfterDelete(unittest.TestCase):
  
      def setUp(self):
          self.conn = None
          self.mock_publish_event = Mock()
          chat_plugin._publish_event = self.mock_publish_event
  
      def record(self):
          return {
              'participant_ids': ['user1', 'user2', 'user3'],
              'admin_ids': ['user1']
          }
  
      def test_publish_event_count_should_be_three(self):
          handle_conversation_after_delete(self.record(), self.conn)
          self.assertIs(self.mock_publish_event.call_count, 3)
  
subject: add test_handle_conversation_after_delete