The jupyter contrib nbextensions Python package contains a code-folding extension that can be enabled within the notebook. Follow the link (Github) for documentation.
To install using command line:
pip install jupyter_contrib_nbextensions
jupyter contrib nbextension install --user
To make life easier in managing them, I’d also recommend the jupyter nbextensions configuratorpackage. This provides an extra tab in your Notebook interface from where you can easily (de)activate all installed extensions.
Installation:
pip install jupyter_nbextensions_configurator
jupyter nbextensions_configurator enable --user