[Bug] fix icl eval with nested list (#632)

opencompass/tasks/openicl_eval.py

@@ -135,13 +135,11 @@ class OpenICLEvalTask(BaseTask):
                         'The prediction for Self-Consistency'
                         'must be list.')
                 if pred_list_flag:
-                    for pred in pred_strs:
-                        pred_strs.append([
-                            self._extract_role_pred(_pred,
-                                                    role.get('begin', None),
+                    pred_strs = [[
+                        self._extract_role_pred(_pred, role.get('begin', None),
                                                 role.get('end', None))
                         for _pred in pred
-                        ])
+                    ] for pred in pred_strs]
                 else:
                     pred_strs = [
                         self._extract_role_pred(pred, role.get('begin', None),