add docstring

matching_series.py

@@ -200,6 +200,7 @@ class matching_series(evaluate.Metric):
         pass
 
     def compute(self, *, predictions=None, references=None, **kwargs) -> Optional[dict]:
+        """"""
         all_kwargs = {"predictions": predictions, "references": references, **kwargs}
         if predictions is None and references is None:
             missing_kwargs = {k: None for k in self._feature_names() if k not in all_kwargs}