human
Solve the following python programming problem given the following code:
def __init__(self, scheme = None, realm = None) : 
    def default_get_password(username) : 
        return None 
def default_auth_error() : 
        return 'Unauthorized Access' 
self.scheme = scheme 
    self.realm = (realm or 'Authentication Required') 
    self.get_password (default_get_password) 
    self.error_handler (<MASK>) 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: realm, self, scheme, default_get_password
assistant
#Here is a proper replacement for <MASK>.
def default_auth_error(