CodeMirror extension crashing JupyterLab

I’ve been trying to update my CodeMirror extension to JupyterLab 4, but when I try to use JupyterLab with my extension installed the screen is blank, and the only clue I get regarding what is wrong is a cryptic “Uncaught (in promise) TypeError: e is undefined” in the console. Can anyone help me figure out what I’m doing wrong?

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