human
Solve the following python programming problem given the following code:
def __call__(self, environ, start_response) : 
    def session_start_response(status, headers, exc_info = None) : 
        if (exc_info is not None) : 
            self.handle_exception (exc_info = exc_info) 
return start_response (status, headers, exc_info) 
try : 
        return self.app (environ, <MASK>) 
except Exception : 
        self.handle_exception (exc_info = sys.exc_info ()) 
        raise 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: self, start_response, environ
assistant
#Here is a proper replacement for <MASK>.
def session_start_response(