Getting attribute error in Dango BaseCommand- Check

I am working on a tutorial project. The same code works for the instructor but doesn't work for me.

I have a file for custom commands:

import time
from psycopg2 import OperationalError as Psycopg2OpError
from django.db.utils import OperationalError
from django.core.management.base import BaseCommand, CommandError

class Command(BaseCommand):

    def handle(self, *args, **options):
        self.stdout.write('waiting for database...')

        db_up = False
        while db_up is False:
            try:
                self.check(databases=['default'])
                db_up = True
            except(Psycopg2OpError, OperationalError):
                self.stdout.write("Database unavailable, waiting 1 second...")
                time.sleep(1)
        
        self.stdout.write(self.style.SUCCESS('Database available!'))

And I am writing test case for the same in a file called test_command.py which is below:

from unittest.mock import patch

from psycopg2 import OperationalError as Psycopg2OpError

from django.core.management import call_command
from django.db.utils import OperationalError
from django.test import SimpleTestCase

@patch('core.management.commands.wait_for_db.Command.Check')
class CommandTests(SimpleTestCase):

    def test_wait_for_db_ready(self, patched_check):
        """test waiting for db if db ready"""
        patched_check.return_value = True

        call_command('wait_for_db')

        patched_check.assert_called_once_with(databases=['default'])

    @patch('time.sleep')
    def test_wait_for_db_delay(self, patched_sleep, patched_check):
        """test waiting for db when getting operational error"""
        patched_check.side_effect = [Psycopg2OpError] * 2 + \
            [OperationalError] * 3 + [True]

        call_command('wait_for_db')
        self.assertEqual(patched_check.call_count, 6)
        patched_check.assert_called_with(databases=['default'])

When I run the tests, I get an error message: