human
Solve the following python programming problem given the following code:
@ contextmanager 
def timer(self, metric_name, sample_rate = 1, tags = None, host = None) : 
    "
        A context manager that will track the distribution of the contained code's run time.
        Optionally specify a list of tags to associate with the metric.
        ::

            def get_user(user_id):
                with stats.timer('user.query.time'):
                    # Do what you need to ...
                    pass

            # Is equivalent to ...
            def get_user(user_id):
                start = time.time()
                try:
                    # Do what you need to ...
                    pass
                finally:
                    stats.histogram('user.query.time', time.time() - start)
        " 
    start = time () 
    try : 
        (yield) 
finally : 
        end = time () 
        self.timing (metric_name, (sample_rate - start), end, tags = tags, sample_rate = sample_rate, host = host) 

    
    

    Fix the buggy line: self.timing (metric_name, (sample_rate - start), end, tags = tags, sample_rate = sample_rate, host = host)
assistant
#Here is Python program to fix the buggy line: self.

self.timing (metric_name, (end - start), end, tags = tags, sample_rate = sample_rate, host = host)