Incompatible with ipynb format when cell.source is [list, of, string]

[Wh1isper]

Description

This is actually jupyter_ydoc's problem, make a note of it here

see: jupyter-server/jupyter_ydoc#111

Reproduce

1. Go to '...'
2. Click on '...'
3. Scroll down to '...'
4. See error '...'

Expected behavior

Context

• Operating System and version:
• Browser and version:
• Jupyter Server version:

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Command Line Output

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Browser Output

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[Wh1isper]

fixed: jupyter-server/jupyter_ydoc#112