get_kline_serial成功创建一个合约k线后，再创建另一个合约就报错

合约为SHFE.cu2509、SHFE.cu2601，duration_seconds为60，2509获取时没错，循环到2601时就报错

for symbol in all_symbols:
                durations = md_cfg.get_symbol_duration(symbol)
                durations = list(filter(lambda x: x, durations.split(',')))
                self.logger.debug(f"durations for '{symbol}': {durations}")
                for d in durations:
                    d = d.strip()
                    duration = int(d)
                    kline = self.api.get_kline_serial(symbol, duration, data_length=600)
                    ...............

出错日志为：

File “/home/royo/mySpace/winctp/ctp/mdsrv.py”, line 110, in start_srv
kline = self.api.get_kline_serial(symbol, duration, data_length=600)
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/tqsdk/api.py”, line 718, in get_kline_serial
if not self.wait_update(deadline=deadline, _task=[task, serial[“df”].__dict__[“_task”]]):
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/tqsdk/api.py”, line 1872, in wait_update
self._run_until_idle(async_run=False)
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/tqsdk/baseApi.py”, line 67, in _run_until_idle
self._run_once()
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/tqsdk/baseApi.py”, line 57, in _run_once
raise self._exceptions.pop(0)
File “/home/royo/mySpace/winctp/ctp/mdsrv.py”, line 41, in save_market_data
dat = pd.read_csv(self.filename, header=None)
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/pandas/util/_decorators.py”, line 311, in wrapper
return func(*args, **kwargs)
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/pandas/io/parsers/readers.py”, line 586, in read_csv
return _read(filepath_or_buffer, kwds)
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/pandas/io/parsers/readers.py”, line 488, in _read
return parser.read(nrows)
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/pandas/io/parsers/readers.py”, line 1047, in read
index, columns, col_dict = self._engine.read(nrows)
File “/home/royo/installed/anaconda3/envs/py37/lib/python3.7/site-packages/pandas/io/parsers/c_parser_wrapper.py”, line 224, in read
chunks = self._reader.read_low_memory(nrows)
File “pandas/_libs/parsers.pyx”, line 801, in pandas._libs.parsers.TextReader.read_low_memory
File “pandas/_libs/parsers.pyx”, line 857, in pandas._libs.parsers.TextReader._read_rows
File “pandas/_libs/parsers.pyx”, line 843, in pandas._libs.parsers.TextReader._tokenize_rows
File “pandas/_libs/parsers.pyx”, line 1925, in pandas._libs.parsers.raise_parser_error
pandas.errors.ParserError: Error tokenizing data. C error: Expected 8 fields in line 67759, saw 13