src/vs/workbench/contrib/notebook/browser/contrib/find/notebookFind.ts/getSearchString
function getSearchString(editor: ICodeEditor, opts: IFindStartOptions) {
	// Get the search string result, following the same logic in _start function in 'vs/editor/contrib/find/browser/findController'
	let searchString = '';
	if (opts.seedSearchStringFromSelection === 'single') {
		const selectionSearchString = getSelectionSearchString(editor, opts.seedSearchStringFromSelection, opts.seedSearchStringFromNonEmptySelection);
		if (selectionSearchString) {
			searchString = selectionSearchString;
		}
	} else if (opts.seedSearchStringFromSelection === 'multiple' && !opts.updateSearchScope) {
		const selectionSearchString = getSelectionSearchString(editor, opts.seedSearchStringFromSelection);
		if (selectionSearchString) {
			searchString = selectionSearchString;
		}
	}
	return searchString;
}