src/vs/workbench/contrib/notebook/common/model/notebookTextModel.ts/NotebookTextModel/_isDocumentMetadataChanged
class NotebookTextModel:	private _isDocumentMetadataChanged(a: NotebookDocumentMetadata, b: NotebookDocumentMetadata) {
		const keys = new Set([...Object.keys(a || {}), ...Object.keys(b || {})]);
		for (let key of keys) {
			if (key === 'custom') {
				if (!this._customMetadataEqual(a[key], b[key])
					&&
					!(this.transientOptions.transientDocumentMetadata[key as keyof NotebookDocumentMetadata])
				) {
					return true;
				}
			} else if (
				(a[key as keyof NotebookDocumentMetadata] !== b[key as keyof NotebookDocumentMetadata])
				&&
				!(this.transientOptions.transientDocumentMetadata[key as keyof NotebookDocumentMetadata])
			) {
				return true;
			}
		}

		return false;
	}