The Jupyter metadata namespace
The cell's name. If present, must be a non-empty string.
The cell's tags. Tags must be unique, and must not contain commas.
Whether the cell is trusted.
This is not strictly part of the nbformat spec, but it is added by the contents manager.
See https://jupyter-server.readthedocs.io/en/latest/operators/security.html.
Cell-level metadata.