code: def test_get_columns_returns_all_columns(self):
      gmail_handler = Mock(GmailHandler)
      gmail_table = EmailsTable(gmail_handler)
      expected_columns = [
          "id",
          "message_id",
          "thread_id",
          "label_ids",
          "sender",
          "to",
          "date",
          "subject",
          "snippet",
          "history_id",
          "size_estimate",
          "body",
          "attachments",
      ]
      self.assertListEqual(gmail_table.get_columns(), expected_columns)
  
imports: from mindsdb.api.executor.data_types.response_type import RESPONSE_TYPE
  from mindsdb.integrations.handlers.gmail_handler.gmail_handler import GmailHandler
  from mindsdb.integrations.handlers.gmail_handler.gmail_handler import EmailsTable
  from google.oauth2.credentials import Credentials
  from mindsdb_sql import parse_sql
  import unittest
  from unittest.mock import Mock, patch
  from unittest import mock
label_desc: Use image node_id 2 for calling the EmailsTableTest obj's underlying member method code with example usage: obj.test_get_columns_returns_all_columns() without return types