Attribute error when loading pickle file in python jupyter notebook

I have created a config file with the following code for an object detection task and saved in the local disk.

# Create the config
C = Config()
C.use_horizontal_flips = horizontal_flips
C.use_vertical_flips = vertical_flips
C.rot_90 = rot_90
C.record_path = record_path
C.model_path = output_weight_path
C.num_rois = num_rois
C.base_net_weights = base_weight_path

with open(config_output_filename, 'wb') as config_f:
pickle.dump(C,config_f)

I am trying to load this pickle file in another jupyter notebook.

with open(config_output_filename, "rb") as f:
C = pickle.load(f)    
# turn off any data augmentation at test time
C.use_horizontal_flips = False
C.use_vertical_flips = False
C.rot_90 = False
print(C.num_rois)

But it gives me the following error.

------------------------------------------------------------------------ 

AttributeError             Traceback (most recent call 
last)
 ipython-input-20-c5528d5ef98b in module
  1 with open(config_output_filename, "rb") as f:
   ---- 2     C = pickle.load(f)

  AttributeError: Can't get attribute 'Config' on module '__main__'

But I was able to load the pickle file from the disk without errors in my previous attempts and applied the configurations on the test set.