Jupyter Notebook error: AttributeError: type object 'IOLoop' has no attribute 'initialized'

AttributeError: type object 'IOLoop' has no attribute 'initialized'

This error may be due to the tornado==5.0* versions. Using Tornado 4.5.3 solves the problem.

To do this, try

pip3 uninstall tornado

pip3 install tornado==4.5.3

This solved my problem. Comment if this is useful to you.