Fix macro accuracy when changing labels (#15379)

* Fix macro accuracy when changing labels

Signed-off-by: He Huang (Steve) <105218074+stevehuang52@users.noreply.github.com>

* Apply isort and black reformatting

Signed-off-by: stevehuang52 <stevehuang52@users.noreply.github.com>

---------

Signed-off-by: He Huang (Steve) <105218074+stevehuang52@users.noreply.github.com>
Signed-off-by: stevehuang52 <stevehuang52@users.noreply.github.com>
Co-authored-by: stevehuang52 <stevehuang52@users.noreply.github.com>

Author: stevehuang52

nemo/collections/asr/models/classification_models.py

@@ -701,6 +701,9 @@ def change_labels(self, new_labels: List[str]):
             if 'test_ds' in self._cfg and self._cfg.test_ds is not None:
                 self._cfg.test_ds.labels = new_labels
 
+            self._macro_accuracy = Accuracy(
+                num_classes=self.decoder.num_classes, top_k=1, average='macro', task='multiclass'
+            )
             logging.info(f"Changed decoder output to {self.decoder.num_classes} labels.")
 
     @classmethod