human
Solve the following python programming problem given the following code:
def check_merge_at(self, a, b) : 
    f = self.timsort.merge_at 
    na = len (a) 
    nb = len (b) 
    orig_keys = ((([42] + a) + b) + [(- 42)]) 
    ssa = 1 
    ssb = (ssa + na) 
    stack_sentinel = MergeRun ((- 42), (- 42)) 
    def run_merge_at(ms, keys, i) : 
        new_ms = f (ms, keys, keys, i) 
        self.assertEqual (keys [0], orig_keys [0]) 
        self.assertEqual (keys [(- 1)], orig_keys [(- 1)]) 
        self.assertSorted (orig_keys [1 : (- 1)], keys [1 : (- 1)]) 
        self.assertIs (new_ms.pending, ms.pending) 
        self.assertEqual (ms.pending [i], (ssa, (na + nb))) 
        self.assertEqual (ms.pending [0], stack_sentinel) 
        return new_ms 
keys = self.array_factory (orig_keys) 
    ms = self.merge_init (keys) 
    ms = self.timsort.merge_append (ms, stack_sentinel) 
    i = ms.n 
    ms = self.timsort.merge_append (ms, MergeRun (ssa, na)) 
    ms = self.timsort.merge_append (ms, MergeRun (ssb, nb)) 
    ms = run_merge_at (orig_keys, keys, i) 
    self.assertEqual (ms.n, (i + 1)) 
    keys = self.array_factory (orig_keys) 
    ms = self.merge_init (keys) 
    ms = self.timsort.merge_append (ms, stack_sentinel) 
    i = ms.n 
    ms = self.timsort.merge_append (ms, MergeRun (ssa, na)) 
    ms = self.timsort.merge_append (ms, MergeRun (ssb, nb)) 
    last_run = MergeRun ((ssb + nb), 1) 
    ms = self.timsort.merge_append (ms, last_run) 
    ms = run_merge_at (ms, keys, i) 
    self.assertEqual (ms.n, (i + 2)) 
    self.assertEqual (ms.pending [(ms.n - 1)], last_run) 

    
    

    Fix the buggy line: ms = run_merge_at (orig_keys, keys, i)
assistant
#Here is Python code to fix the buggy line: ms = run_merge_at (orig_keys, keys, i)
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ms = run_merge_at (ms, keys, i)