asserts replaced by exception for text classification task with test. (…

…#3256)

* asserts replaced by exception for text classification task with test.

* Update tests/test_tasks.py

Co-authored-by: Quentin Lhoest <42851186+lhoestq@users.noreply.github.com>

src/datasets/tasks/text_classification.py

@@ -18,7 +18,8 @@ class TextClassification(TaskTemplate):
 
     def __post_init__(self):
         if self.labels:
-            assert len(self.labels) == len(set(self.labels)), "Labels must be unique"
+            if len(self.labels) != len(set(self.labels)):
+                raise ValueError("Labels must be unique")
             # Cast labels to tuple to allow hashing
             self.__dict__["labels"] = tuple(sorted(self.labels))
             self.__dict__["label_schema"] = self.label_schema.copy()

tests/test_tasks.py

@@ -40,6 +40,13 @@ def test_from_dict(self):
         self.assertEqual(input_schema, task.input_schema)
         self.assertEqual(label_schema, task.label_schema)
 
+    def test_value_error_unique_labels(self):
+        with self.assertRaises(ValueError):
+            # Add duplicate labels
+            labels = self.labels + self.labels[:1]
+            task = TextClassification(text_column="input_text", label_column="input_label", labels=labels)
+            self.assertEqual("text-classification", task.task)
+
 
 class QuestionAnsweringTest(TestCase):
     def test_column_mapping(self):