(Deprecated) Installing extensions with the jupyter labextension install command is now deprecated and will be removed in a future major version of JupyterLab.
Users should manage prebuilt extensions with package managers like pip and conda, and extension authors are encouraged to distribute their extensions as prebuilt packages
Installing jupyter lab extensions should now be done with pip or conda:
~$ jupyter labextension install "@systems-modeling/jupyterlab-sysml"