fix

Author: HydrogenSulfate

ppsci/metric/base.py

@@ -18,6 +18,6 @@
 class Metric(nn.Layer):
     """Base class for metric."""
 
-    def __init__(self, keep_batch: str = False):
+    def __init__(self, keep_batch: bool = False):
         super().__init__()
         self.keep_batch = keep_batch