human
Solve the following python programming problem given the following code:
@gen.engine
def ProcessFiles(merged_store, logs_paths, filenames, callback):
assistant
#Here is the Python program you requested.

    """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('\n')
            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('SUCCESS'):
                    parsed = logs_util.ParseSuccessMsg(msg)
                    if (not parsed):
                        continue
                    (user, device, op, class_name, method_name)...