Extract concat_results function

src/results.py

@@ -48,11 +48,16 @@ async def load_results_dataframes(*model_ids, result_paths_per_model=None):
     return result
 
 
-def display_results(task, hide_std_errors, show_only_differences, *dfs):
+def concat_results(dfs):
     dfs = [df.set_index("index") for df in dfs if "index" in df.columns]
-    if not dfs:
+    if dfs:
+        return pd.concat(dfs)
+
+
+def display_results(task, hide_std_errors, show_only_differences, *dfs):
+    df = concat_results(dfs)
+    if df is None:
         return None, None
-    df = pd.concat(dfs)
     df = df.T.rename_axis(columns=None)
     return (
         display_tab("results", df, task, hide_std_errors=hide_std_errors),