Update metrics.py

Changed from lambda expression which pylint doesn't like.

Author: davidtweedle

algoperf/workloads/ogbg/metrics.py

@@ -31,6 +31,9 @@ class MeanAveragePrecision(
     metrics.CollectingMetric.from_outputs(('logits', 'labels', 'mask'))):
   """Computes the mean average precision (mAP) over different tasks."""
 
+  def sigmoid_np(x):
+    return 1 / (1 + np.exp(-x))
+
   def compute(self):
     # Matches the official OGB evaluation scheme for mean average precision.
     values = super().compute()
@@ -49,7 +52,7 @@ def compute(self):
         dist.all_gather(all_tensors, tensor)
         all_values[idx] = torch.cat(all_tensors).cpu().numpy()
       labels, logits, mask = all_values
-      sigmoid = lambda x: 1 / (1 + np.exp(-x))
+      sigmoid = sigmoid_np
 
     mask = mask.astype(bool)