Remove unused import.
Remove unused import.

jupyter/jupyter-js-notebook,blink1073/jupyter-js-notebook,blink1073/jupyter-js-notebook,blink1073/jupyter-js-notebook,blink1073/jupyter-js-notebook,jupyter/jupyter-js-notebook,jupyter/jupyter-js-notebook,jupyter/jupyter-js-notebook,jupyter/jupyter-js-notebook,blink1073/jupyter-js-notebook