How to use it in jupyter notebook?

notebook code：
```
from ml_collections import config_flags
_CONFIG = config_flags.DEFINE_config_file('config')
mp.set_start_method('spawn')

params = _CONFIG.value
```
get an error:
```
---------------------------------------------------------------------------
UnparsedFlagAccessError Traceback (most recent call last)
Cell In[2], line 5
2 _CONFIG = config_flags.DEFINE_config_file('config')
3 mp.set_start_method('spawn')
----> 5 params = _CONFIG.value

File ~/anaconda3/envs/LLM/lib/python3.11/site-packages/absl/flags/_flagvalues.py:1376, in FlagHolder.value(self)
1365 @property
1366 def value(self):
1367 """Returns the value of the flag.
1368
1369 If ``_ensure_non_none_value`` is ``True``, then return value is not
(...)
1374 IllegalFlagValueError: if value is None unexpectedly.
1375 """
-> 1376 val = getattr(self._flagvalues, self._name)
1377 if self._ensure_non_none_value and val is None:
1378 raise _exceptions.IllegalFlagValueError(
1379 'Unexpected None value for flag %s' % self._name)

File ~/anaconda3/envs/LLM/lib/python3.11/site-packages/absl/flags/_flagvalues.py:481, in FlagValues.__getattr__(self, name)
479 return fl[name].value
480 else:
--> 481 raise _exceptions.UnparsedFlagAccessError(
482 'Trying to access flag --%s before flags were parsed.' % name)

UnparsedFlagAccessError: Trying to access flag --config before flags were parsed.
```