diff --git a/intake_esm/cat.py b/intake_esm/cat.py
index c6a2de5e..463ad471 100644
--- a/intake_esm/cat.py
+++ b/intake_esm/cat.py
@@ -266,11 +266,7 @@ def columns_with_iterables(self) -> set[str]:
         if self._df.empty:
             return set()
         has_iterables = (
-            self._df.sample(20, replace=True)
-            .map(type)
-            .isin([list, tuple, set])
-            .any()
-            .to_dict()
+            self._df.sample(20, replace=True).map(type).isin([list, tuple, set]).any().to_dict()
         )
         return {column for column, check in has_iterables.items() if check}