Update keras_rs/src/losses/lambda_weights.py

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: LakshmiKalaKadali

keras_rs/src/losses/lambda_weights.py

@@ -154,7 +154,7 @@ def pair_weights(self, labels, ranks):
         """
         raise NotImplementedError('Calling an abstract method.')
 
-    #@abc.abstractmethod
+    @abc.abstractmethod
     def individual_weights(self, labels, ranks):
         """Returns the weight tensor for individual examples.
 
@@ -166,7 +166,7 @@ def individual_weights(self, labels, ranks):
         Returns:
             A tensor that can weight individual examples with shape [batch_size, list_size].
         """
-        return labels
+        raise NotImplementedError('Calling an abstract method.')
 
 class LabelDiffLambdaWeight(LambdaWeight):
   """A simple LambdaWeight to compute the pair label difference."""