How to solve AttributeError: module 'cv2' has no attribute 'gapi_wip_gst_GStreamerPipeline'

#python  3.7.0  
#opencv-contrib-python 4.5.5.62   
#Ubuntu  16.04  
#conda   4.5.12

I am trying to do python3 project.py to run a python file,
then I got the AttributeError: module 'cv2' has no attribute 'VideoCapture'

Then I try sudo python3 project.py to run,
it became : AttributeError: module 'cv2' has no attribute 'gapi_wip_gst_GStreamerPipeline'

How can I solve these two errors, especially the second one.
And what's the differences between python3 project.py and sudo python3 project.py?

Thanks.