support empty kwargs

Signed-off-by: sichu <[email protected]>

sub-packages/bionemo-llm/src/bionemo/llm/model/config.py

@@ -162,9 +162,14 @@ class MetricConfig:
     """
 
     class_path: str
-    kwargs: dict[str, Any]
+    kwargs: Optional[dict[str, Any]] = None
     metric_name: Optional[str] = None
 
+    def __post_init__(self):
+        """__post_init__ in dataclass."""
+        super().__post_init__()
+        self.kwargs = {} if self.kwargs is None else self.kwargs
+
     def get_instance(self) -> torchmetrics.Metric:
         """Dynamically imports and instantiates the metric class."""
         module_path, class_name = self.class_path.rsplit(".", 1)