plot_helper.py outdated for JupyterLab

[labarba]

Trying to run a plot command from plot_helper.py in a recent installation (JupyterLab) gives the error:

Javascript Error: Can't find variable: IPython

This typically occurs when trying to use an IPython-specific feature or functionality in a JupyterLab environment where IPython is not directly accessible.

In JupyterLab, the underlying architecture and the way it interacts with JavaScript have changed compared to the classic Jupyter Notebook interface. IPython, which provides the interactive computing environment in Jupyter Notebook, is not directly available in JupyterLab in the same way.

TO DO: plot_helper.py needs to be updated to be compatible with JupyterLab's architecture.

@tingyu66 — If you have some hints on where updates are needed in the script, let me know!