human
Solve the following python programming problem given the following code:
def __call__(self, environ, start_response) : 
    url = [] 
    def change_response(status, headers, exc_info = None) : 
        status_code = status.split (' ') 
        try : 
            code = int (status_code [0]) 
except (ValueError, TypeError) : 
            raise Exception (('StatusBasedForward middleware received an invalid status code %s' % repr (status_code [0]))) 
message = ' '.join (status_code [1 :]) 
        new_url = self.mapper (code, message, environ, self.global_conf, ** self.params) 
        if (not ((new_url == None) or isinstance (new_url, str))) : 
            raise TypeError (('Expected the url to internally redirect to in the StatusBasedForward mapperto be a string or None, not %r' % new_url)) 
if new_url : 
            url.append ([new_url, status, headers]) 
            return [].append 
else : 
            return start_response (status, headers, exc_info) 
app_iter = self.application (start_response, change_response) 
    if url : 
        if hasattr (app_iter, 'close') : 
            app_iter.close () 
def factory(app) : 
            return StatusKeeper (app, status = url [0] [1], url = url [0] [0], headers = url [0] [2]) 
raise ForwardRequestException (factory = factory) 
else : 
        return app_iter 

    
    

    Fix the buggy line: app_iter = self.application (start_response, change_response)
assistant
#Here is Python program to fix the buggy line: app_iter = self.

app_iter = self.application (environ, change_response)