human
Solve the following python programming problem given the following code:
@ defer.inlineCallbacks 
def test_authentication_required_with_tls(self) : 
    processor = FakeProcessor () 
    processor_dependency = dependencies.InstanceDependency (processor) 
    processor_dependency.is_ready = True 
    self.runtime_environment.configure () 
    data_dir = filepath.FilePath (__file__).sibling ('data') 
    self.create_smtp_server (tls = dict (private_key = data_dir.child ('server.key').path, certificate = data_dir.child ('server.crt').path), checker = dict (name = 'twisted.cred.checkers.InMemoryUsernamePasswordDatabaseDontUse', arguments = dict (username = 'password'))) 
    self.application.startService () 
    self.addCleanup (self.application.stopService) 
    self.server.processor_dependency = self.processor_dependency 
    def do_test_with_tls() : 
        smtp = smtplib.SMTP ('localhost', self.port, timeout = 1) 
        self.addCleanup (threads.deferToThread, smtp.quit) 
        self.assertSMTPErrorCode (550, smtp.sendmail, 'foo@foo.com', 'bar@bar.com', 'Hello') 
        self.assertSMTPErrorCode (530, smtp.login, 'username', 'password') 
        smtp.starttls () 
        self.assertSMTPErrorCode (550, smtp.sendmail, 'foo@foo.com', 'bar@bar.com', 'Hello') 
        self.assertSMTPErrorCode (535, smtp.login, 'invalid', 'invalid') 
        self.assertSMTPErrorCode (535, smtp.login, 'username', 'invalid') 
        self.assertSMTPErrorCode (535, smtp.login, 'invalid', 'password') 
        smtp.login ('username', 'password') 
        smtp.sendmail ('foo@foo.com', 'bar@bar.com', 'Hello') 
(yield threads.deferToThread (<MASK>)) 
    self.assertEquals (len (self.processor.batons), 1) 
    baton = self.processor.batons [0] 
    self.assertEquals (baton ['from_addr'], 'foo@foo.com') 
    self.assertEquals (baton ['to_addr'], 'bar@bar.com') 
    self.assertEquals (baton ['avatar_id'], 'username') 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def do_test_with_tls(