Error while running Detectron2 code through spyder

I am able to execute the Detectron2 script once but the next time I try to run it I get this error. It works once after I restart the kernel.

```
File "/home/user/anaconda3/lib/python3.7/site-packages/spyder_kernels/customize/spydercustomize.py", line 827, in runfile
execfile(filename, namespace)

File "/home/user/anaconda3/lib/python3.7/site-packages/spyder_kernels/customize/spydercustomize.py", line 110, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)

File "/home/user/Table_Structure_Extract/Detectron2/detectron2/detectron2/Scripts/Table_Instance1.py", line 23, in
from detectron2.engine import DefaultTrainer

File "/home/user/Prateek_Data/Table_Structure_Extract/Detectron2/detectron2/detectron2/engine/__init__.py", line 12, in
from .defaults import *

File "/home/user/Table_Structure_Extract/Detectron2/detectron2/detectron2/engine/defaults.py", line 23, in
from detectron2.checkpoint import DetectionCheckpointer

File "/home/user/Table_Structure_Extract/Detectron2/detectron2/detectron2/checkpoint/__init__.py", line 6, in
from . import catalog as _UNUSED # register the handler

File "/home/user/Table_Structure_Extract/Detectron2/detectron2/detectron2/checkpoint/catalog.py", line 133, in
PathManager.register_handler(ModelCatalogHandler())

File "/home/user/anaconda3/lib/python3.7/site-packages/fvcore/common/file_io.py", line 768, in register_handler
assert prefix not in PathManager._PATH_HANDLERS

AssertionError
```