human
Create a short git commit message for the following git diff patch:

diff --git a/calmpy/helper/functions.py b/calmpy/helper/functions.py
index b567a69c..1d881733 100644
--- a/calmpy/helper/functions.py
+++ b/calmpy/helper/functions.py
@@ -270,18 +270,25 @@ def load_json_unpacked(
     return r_df
 
 
-def _count_empty_lists(s: pl.Series):
+def _count_empty_lists(s: pl.Series) -> int:
     """
     counts the number of empty lists in the column
     """
-    return sum(1 for _c in s if isinstance(_c, list) and len(_c) > 0)
+    if s.dtype == pl.List:
+        return s.apply(lambda x: 1 if x.is_empty() else 0).sum()
+    return 0
 
 
-def _drop_empty(df: pl.DataFrame):
+def _drop_empty(df: pl.DataFrame) -> pl.DataFrame:
     """
     drop columns which contains only none or empty list values
     """
-    return df[:, [not (s.null_count() == df.height or _count_empty_lists(s) == 0) for s in df]]
+    cols_to_drop = set()
+    for series in df:
+        if series.null_count() == df.height or _count_empty_lists(series) == df.height:
+            cols_to_drop.add(series.name)
+
+    return df.drop(list(cols_to_drop))
 
 
 def get_dtypes(elt: list, data_types: set = None) -> set:
diff --git a/tests/calmpy/codebeamer/test_itemlist.py b/tests/calmpy/codebeamer/test_itemlist.py
index 604f428e..13e1853c 100644
--- a/tests/calmpy/codebeamer/test_itemlist.py
+++ b/tests/calmpy/codebeamer/test_itemlist.py
@@ -63,3 +63,20 @@ class TestItemList(ServerWithLessRetriesTestCase):
         items = tracker.get_items()
         df 
gpt
--- Reasoning ---
1. Is the question multiple-choice question?
No
2. Is it implied multiple-choice question?
No
3. If two experts were independently asked the question, will the final answer be exactly the same?
No

--- Answer ---
open