human
Solve the following python programming problem given the following code:
@ gen.engine 
def ProcessFiles(merged_store, logs_paths, filenames, callback) : 
    "Fetch and process each file contained in 'filenames'." 
    def _ProcessOneFile(contents, day_stats, device_entries, trace_entries) : 
        'Iterate over the contents of a processed file: one entry per line. Increment stats for specific entries.' 
        buf = cStringIO.StringIO (contents) 
        buf.seek (0) 
        context_before = deque (maxlen = (options.options.trace_context_num_lines + 1)) 
        pending_traces = [] 
        def _AddTrace(trace_type, timestamp, module, message) : 
            trace = { 
                'type' : trace_type, 
                'timestamp' : timestamp, 
                'module' : module, 
                'trace' : msg, 
                'context_before' : list (context_before) [: (- 1)], 
                'context_after' : [], 
} 
            if (options.options.trace_context_num_lines == 0) : 
                trace_entries.append (trace) 
else : 
                pending_traces.append (trace) 
def _CheckPendingTraces(line) : 
            for t in pending_traces : 
                t ['context_after'].append (line) 
while (pending_traces and (len (pending_traces [0] ['context_after']) >= options.options.trace_context_num_lines)) : 
                trace_entries.append (pending_traces.pop (0)) 
while True : 
            line = buf.readline () 
            if (not line) : 
                break 
line = line.rstrip ('
') 
            context_before.append (line) 
            _CheckPendingTraces (line) 
            parsed = logs_util.ParseLogLine (line) 
            if (not parsed) : 
                continue 
(day, time, module, msg) = parsed 
            timestamp = logs_util.DayTimeStringsToUTCTimestamp (day, time) 
            if (options.options.process_traceback and re.search (kTracebackRE, line)) : 
                _AddTrace ('traceback', timestamp, module, msg) 
if (module.startswith ('user_op_manager:') or module.startswith ('operation:')) : 
                if msg.startswith...

    
    

    Fix the buggy line: day = logs_paths.MergedLogPathToDate (last_day_written)
assistant
#Here is Python program to fix the buggy line: day = logs_paths.

day = logs_paths.MergedLogPathToDate (filename)